For the scores of immigrants who arrived at the US border in a caravan denounced by Donald Trump, an arduous journey north has shifted into an odyssey through America’s asylum system.

More than 100 Central American immigrants arrived at the San Ysidro border crossing to seek safe haven from violence in their home countries, organisers said, pointing to post-election chaos in Honduras in particular.

But in a sign of the uphill struggle ahead, most were prevented from applying for asylum as officials said the border station had already reached capacity. Many spent the night sleeping on the ground.

A US Customs and Border Patrol official did not respond to a request to confirm how many of the asylum-seekers had been processed or lay out a timeline.

Mr Trump has long railed against the asylum process as an overly lenient conduit for illegal immigration. The president picked up that theme again in a speech over the weekend, calling America’s system “the dumbest immigration laws anywhere on earth”.

“They know once they get here they can walk right into our country,” Mr Trump said. “If they can get anywhere near, if they touch our ground, it’s ‘welcome to the United States’.”

Protestors rally at JFK Airport against Muslim immigration ban Show all 20 1 /20 Protestors rally at JFK Airport against Muslim immigration ban Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-1 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-2 Protestors rally during a protest against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump singed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-3 Protestors rally during a protest against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump singed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-4 SAN FRANCISCO, CA - JANUARY 28: Demonstrators hold signs during a rally against a ban on Muslim immigration at San Francisco International Airport on January 28, 2017 in San Francisco, California. President Donald Trump signed an executive order Friday that suspends entry of all refugees for 120 days, indefinitely suspends the entries of all Syrian refugees, as well as barring entries from seven predominantly Muslim countries from entering for 90 days. Stephen Lam/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-5 A crowd of protesters gathers outside of the Brooklyn Federal Courthouse as a judge hears a challenge against President Donald Trump's executive ban on immigration from several Muslim countries, on January 28, 2017 in Brooklyn. The judge issued an emergency stay on part of Trump's executive order, ruling that sending refugees stopped at U.S. airports back to their countries would be harmful. Yana Paskova/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-6 Protestors rally during a demonstration against the new immigration ban issued by President Donald Trump at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-7 NEW YORK, NY - JANUARY 28: Protestors rally during a demonstration against the new immigration ban issued by President Donald Trump at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-8 Protestors rally during a demonstration against the new immigration ban issued by President Donald Trump at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-9 NEW YORK, NY - JANUARY 28: Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. (Photo by Stephanie Keith/Getty Images) Getty Images Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-10 NEW YORK, NY - JANUARY 28: Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. (Photo by Stephanie Keith/Getty Images) Getty Images Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-11 NEW YORK, NY - JANUARY 28: Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-12 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-13 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-14 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-15 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-16 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-17 NEW YORK, NY - JANUARY 28: Protestors rally during a protest against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump singed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-18 Protestors rally during a protest against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump singed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-19 Protestors rally during a protest against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump singed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-20 Passengers wait in line to check in at the American Airlines terminal at JFK International Airport August 10, 2006 in the Queens borough of New York City. British authorities arrested 21 people and halted a anallegedly terrorist plot to use liquid explosives concealed in carry-on luggage to blow up airliners traveling between Britain and the U.S. Homeland Security chief Michael Chertoff said that the plot appeared to be directed at U.S. carriers flying out of Heathrow. such as United Airlines, American Airlines, Continental Airlines. Stephen Chernin/Getty

But some immigration law experts argue protections for asylum-seekers have already eroded under the Trump administration, and activists who back the caravan accused the federal government of neglecting its duties in not swiftly processing the newly arrived batch of immigrants.

“Stop rejecting asylum-seekers who try to present themselves at the port of entry”, organiser and immigration attorney Nicole Ramos said in a speech. “You know what you’re doing, you know you turn people away. You complain they are breaking the law by entering illegally – you are breaking the law”.

Migrant 'caravan' gathers at the US-Mexico border

Echoing that criticism, Rep Zoe Lofgren told CNN that people with a legitimate argument for asylum “have a right to present their case”.

“That’s not a violation of immigration law. That’s a part of immigration law”, said Ms Lofgren, a Democrat representing California.

Immigrants who claim asylum at ports of entry are typically detained until an interview in which they must prove they have a “credible fear” of persecution in their home countries. Those who meet that standard win the right to make a formal asylum application to an immigration judge.

“It’s still a majority of [Central American] immigrants who are passing this initial screening test”, said Niels Frenzen, director of the immigration law clinic at the University of Southern California, but once they end up before a judge, the vast majority are denied.

Officials in the Trump administration have warned that immigrants are exploiting the asylum system. Department of Homeland Security secretary Kirstjen Nielsen prefaced the caravan’s arrival by vowing to prosecute immigrants who make false claims and warning that “smugglers, traffickers, and criminals understand our legal loopholes better than Congress”. Attorney General Jeff Sessions called the caravan “a deliberate attempt to undermine our laws and overwhelm our system”.

Against that backdrop, immigration attorneys say they have noticed a marked difference in how often immigrants in asylum proceedings are detained. A lawsuit filed earlier this year accused the Trump administration of indefinitely detaining asylum-seekers who had credible cases and posed no flight risk.

The fates of caravan members in the coming weeks could depend in part on their age and family status.

Unaccompanied minors who cross the border are detained in separate facilities administered by the Office of Refugee Resettlement and enjoy more leniency in being released to family members. Mothers with children could end up at family detention centres in Texas and Pennsylvania, while older family members or men “could end up anywhere”, Mr Frenzen said.

And there’s a greater chance that people are detained, according to Mr Frenzen. He said that administration threats to prosecute parents who facilitate children’s journeys north have had a “definite chilling effect”, paralleling a larger crackdown.