WASHINGTON — The Trump administration introduced new measures Thursday to deny asylum to migrants who enter the country illegally, invoking national security powers to curb long-standing humanitarian protections for foreigners arriving on American soil.

The restrictions will invoke authorities used by President Trump to implement his “travel ban” in early 2017, according to senior administration officials who outlined them, and apply indefinitely.

The measures are expected to face swift legal challenges. Immigrant advocacy groups insist that U.S. laws clearly extend asylum protections to anyone who reaches the United States and expresses a fear of persecution, no matter how they enter the country.

Administration officials said the Supreme Court has upheld the president’s broad executive powers on such matters and that the restrictions rolled out Thursday represent a reasonable response as the nation’s immigration system is drowning in what they characterized as frivolous asylum claims by migrants who cross illegally.

“Those who enter the country between (official) ports of entry – i.e. illegally – are knowingly and voluntarily breaking the law,” one administration official said. “So it’s just important to remind everybody that while all immigration laws do afford people various forms of protection, the reality is that it’s a violation of federal law to enter our country in the manner that these illegal aliens are entering the country.”

Trump is preparing to issue a proclamation asserting the emergency powers, and the rule changes will be published Friday in the Federal Register, according to the officials, who spoke with the media in a conference call on condition of anonymity.

These asylum restrictions mark the administration’s latest attempt to prevent immigrants and foreigners from entering the United States. Thursday’s announcement comes as an estimated 7,000 to 10,000 Central Americans move north through Mexico in caravan groups. Trump has demanded new tools to stop them from entering the United States and ordered the deployment of thousands of U.S. troops to back up border agents.

“Our nation is experiencing an unprecedented crisis on our Southern Border,” the Department of Homeland Security said in a statement. “Low standards for claiming a fear of persecution have allowed aliens with meritless claims to illegally enter our country.”