A group of Central American migrants seeking asylum in the U.S. may not be able to enter the country on Sunday because the border crossing near San Diego, Calif., was already at capacity, U.S. authorities said.

U.S. Customs and Border Patrol said the San Ysidro crossing in San Diego already hit its maximum number of people -- 300 -- before the caravan of roughly 200 Central Americans arrived.

As a result, those seeking asylum in the U.S. may not be able to enter the country on Sunday, a spokesman for the organization said. Instead, they will remain on the other side of the border, near Tijuana, Mexico.

"As sufficient space and resources become available, CBP officers will be able to take additional individuals into the port for processing," said CBP Commissioner Kevin McAleenan in the statement. "CBP will communicate with Mexican authorities for operational awareness on this issue of capacity within CBP facilities as appropriate."

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The so-called caravan has been heading toward the U.S. for weeks and is made up of the first batch of asylum seekers who arrived at the border on Thursday. The group is expected to try entering the U.S. at a border crossing. 

The asylum seekers will present one of the first major tests to the Trump administration's migration policies. 

On Thursday, Homeland Security Secretary Kirstjen NielsenKirstjen Michele NielsenActing DHS secretary says he expects Russia to attempt to interfere in 2020 elections House Homeland Security rip DHS's 'unacceptable' failure to comply with subpoena Trump puts Kushner in charge of overseeing border wall construction: report MORE said the federal government is prepared to prosecute migrants in the caravan. 

"Let me be clear: We will enforce the immigration laws as set forth by Congress," Nielsen said. 

"If you enter our country illegally, you have broken the law and will be referred for prosecution. If you make a false immigration claim, you have broken the law and will be referred for prosecution. If you assist or coach an individual in making a false immigration claim, you have broken the law and will be referred for prosecution."

Nielsen has urged the migrants to seek protection in the first country they entered since leaving their homes, including in Mexico, instead of moving through to the U.S. 

President TrumpDonald John TrumpRouhani says Iran will never seek nuclear weapons Trump downplays seriousness of injuries in Iran attack after US soldiers treated for concussions Trump says Bloomberg is 'wasting his money' on 2020 campaign MORE has railed against the caravan, tweeting last week that he directed Nielsen to block the migrants.

"Despite the Democrat inspired laws on Sanctuary Cities and the Border being so bad and one sided, I have instructed the Secretary of Homeland Security not to let these large Caravans of people into our Country. It is a disgrace," he tweeted. "We are the only Country in the World so naive!"

Updated on April 29, 2018, at 6:10 p.m.