Biden said the vast majority of migrants caught at the U.S.-Mexico border are turned back but that some families had been allowed into the country because Mexico would not accept their return.
Biden, a Democrat, also argued that the overall increase in border arrests was part of a seasonal trend that had happened under former President Donald Trump, a Republican.
The number of migrants caught at the U.S.-Mexico border has climbed in recent weeks, thrusting Biden into an emerging humanitarian and political crisis a little more than two months after he took office.
The Biden administration has struggled to house a rising number of unaccompanied minors caught at the border. As of Tuesday, nearly 5,000 children were backed up in crowded border stations awaiting transfers to overwhelmed federal shelters.
Republicans contend Biden encouraged more migrants to cross illegally when he rolled back some of Trump's restrictive policies. At the same time, some Democrats have criticized the conditions in facilities used to hold migrant children and called for children to be released faster.
U.S. Border Patrol caught roughly 100,000 migrants at the border in February, the highest monthly level since a surge in mid-2019. Homeland Security Secretary Alejandro Mayorkas said last week that border crossings are on pace for the highest level in 20 years.