The United States is cutting off aid to El Salvador, Guatemala and Honduras, known collectively as the "Northern Triangle," the State Department said on Saturday, a day after President Donald Trump blasted the Central American countries for sending migrants to the United States.

"We are carrying out the President's direction and ending FY (fiscal year) 2017 and FY 2018 foreign assistance programmes for the Northern Triangle," a State Department spokesperson said in a statement. The department declined to provide further details.

The State Department said it would "engage Congress in the process," an apparent acknowledgement that it will need lawmakers' approval to end the funding.

A US House Appropriations Committee aide estimated that around $700 million of aid was affected.

Democratic Representative Nita Lowey, who chairs the committee, tweeted that the move to cut aid was "immoral and more likely to deteriorate conditions that push people into the kind of poverty and despair that exacerbates migration."

New Jersey Senator Bob Menendez, the top Democrat on the Senate Foreign Relations Committee, called Trump's order a "reckless announcement" and urged Democrats and Republicans alike to reject it.

"U.S. foreign assistance is not charity; it advances our strategic interests and funds initiatives that protect American citizens," Menendez said in a statement.

Trump claimed on Friday during a trip to Florida that the countries had "set up" caravans of migrants in order to export them into the United States. A surge of asylum seekers from the three countries have sought to enter the United States across its southern border in recent days.

"We were giving them $500 million. We were paying them tremendous amounts of money, and we're not paying them anymore because they haven't done a thing for us," Trump said.

Trump also threatened on Friday to close the US border with Mexico next week if Mexico does not stop immigrants from reaching the United States, a move that could disrupt millions of legal border crossings and billions of dollars in trade.