Update, Monday, 4:35 p.m.:
President Donald Trump says a caravan of Central American migrants seeking asylum in the U.S. shows the weakness of the nation's immigration laws.

Reacting to news that the group reached the U.S. border over the weekend, Trump tweeted Monday that the group is "openly defying our border."

He called out Democrats for supporting "sanctuary city" policies that limit local police cooperation with federal immigration authorities.

Trump and other members of his administration have been watching and criticizing the caravan of hundreds of Central Americans since they started journeying through Mexico a month ago.

The migrants tried to start applying for protection at the San Diego border crossing Sunday. But U.S. officials have said for two days that the facility is full and can't accommodate them.

Update, Monday, 12:00 p.m.:
About 200 people in a caravan of Central American asylum seekers waited on the Mexican border with San Diego for a second straight day on Monday to turn themselves in to U.S. border inspectors, who said the nation's busiest crossing facility did not have enough space to accommodate them.

After a monthlong journey across Mexico under the Trump administration's watchful eye, the asylum seekers faced an unexpected twist Sunday when U.S. Customs and Border Protection Commissioner Kevin McAleenan said San Diego's San Ysidro border crossing facility had "reached capacity." The agency said in a statement on Monday that it had no estimate when the location would accept new asylum application cases.

Original post:
A group of Central Americans who journeyed to the U.S. border in a caravan resolved to turn themselves in and ask for asylum Sunday in a direct challenge to the Trump administration — only to have U.S. immigration officials announce that the San Diego crossing was already at capacity and wouldn't immediately be accepting them.

Nearly 200 migrants, many traveling with children, had decided to apply for protection at San Diego's San Ysidro border crossing, organizers said. The caravan got attention after President Donald Trump and members of his Cabinet called it a threat to the United States.

Shortly before the migrants were expected to arrive, U.S. Customs and Border Protection said San Diego's San Ysidro crossing would not immediately be able to handle more asylum seekers. It can hold about 300 people at a time, and officials had been warning that it might fill up.

"At this time, we have reached capacity at the San Ysidro port of entry for CBP officers to be able to bring additional persons traveling without appropriate entry documentation into the port of entry for processing," Commissioner Kevin McAleenan said in a statement. "Those individuals may need to wait in Mexico as CBP officers work to process those already within our facilities."

He said the crossing could take in additional people as space and resources become available. Despite the news, about 200 migrants still started walking toward the port.

Rodulfo Figueroa, the top Mexican immigration official in Baja California state, told caravan organizers to send in an initial group of 20 migrants to see if U.S. border inspectors would entertain their request for asylum.

Figueroa said he doesn't know if they would be allowed in and had not received word from U.S. immigration officials.

Nicole Ramos, an attorney working on behalf of caravan members, expressed disbelief that U.S. authorities cannot process more asylum seekers until its backlog eases.

"They have been well aware that a caravan is going to arrive at the border," she said at a news conference. "The failure to prepare and failure to get sufficient agents and resources is not the fault of the most vulnerable among us. We can build a base in Iraq in under a week. We can't process 200 refugees. I don't believe it."

The migrants had made their way north by foot, freight train and bus over the past month, many of them saying they feared for their lives in their home countries.

The Trump administration has been tracking the caravan since it started in Mexico on March 25 near the Guatemala border. Attorney General Jeff Sessions has called the caravan "a deliberate attempt to undermine our laws and overwhelm our system."

Attorney General Jeff Sessions called the caravan "a deliberate attempt to undermine our laws and overwhelm our system," pledging to send more immigration judges to the border to resolve cases if needed.

Trump administration officials have railed against what they call "catch-and-release" policies that allow people requesting asylum to be released from custody into the U.S. while their claims make their way through the courts in a process that can last a year.

Earlier Sunday, the migrants boarded five old school buses to attend a rally at a Pacific Ocean beach, with supporters gathering on both sides of the border fence and some climbing the barrier to sit or to wave signs.

Wendi Yaneri Garcia said she is confident she will be released while her asylum case wends its way through the courts because she is traveling alone with her 2-year-old son, who has been sick.

"All I want is a place where I can work and raise my son," the 36-year-old said.

She said that police in her hometown of Atlantida, Honduras, jailed her for protesting construction of a hydroelectric plant and that she received death threats after being released.

Nefi Hernandez, 24, said a gang in his hometown of San Pedro Sula, Honduras, threatened to kill him and his family if he did not sell drugs. He intended to seek asylum with his wife and baby daughter, who was born on the journey through Mexico.

Jose Cazares, 31, said he faced death threats in the Honduran city of Yoro because a gang member suspected of killing the mother of his children learned one of his Cazares' sons reported the crime to police.

"One can always make up for lost time with a child, but if they kill him, you can't," he said outside his dome-shaped tent in a migrant shelter near the imposing U.S. border barriers separating San Diego from Tijuana.

But the travelers face an uncertain future if they ask for asylum. U.S. immigration lawyers warned them that they face possible separation from their children and detention for many months.

Homeland Security Secretary Kirstjen Nielsen said that asylum claims will be resolved "efficiently and expeditiously" but that the asylum-seekers should seek it in the first safe country they reach, including Mexico.

She warned that any asylum seekers making false claims to U.S. authorities could be prosecuted, as could anyone who assists or coaches immigrants on making false claims.

Administration officials and their allies claim that asylum fraud is growing and that many who seek it are coached on how to do so.

Asylum-seekers are typically held up to three days at the border and then turned over to U.S. Immigration and Customs Enforcement. If they pass an asylum officer's initial screening, they may be detained or released into the U.S. with ankle monitors.

Nearly 80 percent of asylum-seekers passed the initial screening from October through December, the latest numbers available, but few are likely to eventually win asylum.

Mexicans fared worst among the 10 countries that sent the largest numbers of U.S. asylum seekers from 2012 to 2017, with a denial rate of 88 percent, according to asylum outcome records tracked by Syracuse University's Transactional Records Action Clearinghouse. El Salvadorans were close behind with a 79 percent denial rate, followed by Hondurans at 78 percent and Guatemalans at 75 percent.

Heather Crone of advocacy group Show Up for Racial Justice says she's found 80 people across the U.S. who agreed to sponsor some of the caravan members if they're released while their petitions are pending.

Asylum seekers are often released to family in the U.S. but some don't have any and seek sponsors.

Evelyn Wiese, a San Francisco immigration attorney, said she tried to make migrants more comfortable sharing memories of the dangers they faced in their homelands.

"It's really scary to tell these experiences to a stranger," Wiese said after counseling a visibly shaken Guatemalan woman at an art gallery in a building that used to house a drug smuggling tunnel into San Diego. "The next time she tells her story will be easier."

Maria de Los Angeles, 17, said she felt confident after speaking with an attorney that U.S. authorities would release her while her case winds its way through court because she was traveling alone with her 1-year-old son. She hoped to move in with a sister in San Francisco.

She said she fled her home in Jutiapa, Honduras, because the father of her son threatened to kill her and their child.

"I'm fired up to go because I believe in God and I believe everything will work out," she said.