WASHINGTON — The incoming chairman of a key oversight committee in the House of Representatives said Sunday that any attempt by President Donald Trump to keep migrants from claiming asylum in the U.S. would be unlawful.

“That’s not the law,” Rep. Elijah Cummings, D-Md., said in an exclusive interview on “Meet the Press,” indicating that Congress will act if the president moves ahead with that policy. “They should be allowed to come in, seek asylum, that's the law."

President Donald Trump has said he’s reached a deal with the government of Mexico to keep migrants traveling in large caravans from Central America in Mexico until their court date to plead asylum. But a spokesman for incoming Mexican President Andrés Manuel López Obrador has said talk of such a deal is premature and U.S. officials told NBC News that the details are still being worked out.

Cummings said he supports the law as it stands. "I think we have a system that has worked for a long time. This president's come in, wants to change it, that's up to him. But now the Congress has got to stand up and hopefully they will," Cummings said.

Family detention at the border and the separation of children from their parents after crossing the border was already on Cummings' list of potential investigations as chair of the House Oversight and Government Reform Committee when Democrats take control of Congress in January.

Cummings has a list of 64 subpoenas it is ready to send to the Trump administration on a variety of issues ranging from immigration to voting rights act, drug prices and the opioid epidemic.

"I think the American people have said that they want checks and balances," Cummings said. "And subpoenas, by the way, that may involve, say, private industries like the pharmaceutical companies" over "these skyrocketing drug prices."

When asked about the priorities he is setting for areas of investigation, Cummings said he will focus on issues that "go to the very heart of our democracy and protecting that democracy."

Cummings also said Sunday that his committee will "probably" look into Trump’s financial ties, especially to Saudi Arabia, and if it violates the emoluments clause, which is aimed at preventing a president from profiting on the office.

Cummings said he wanted to determine "whether the president is acting in his best interest or those of the American people," adding, "I think this would be appropriate and there are other committees that will be looking at this too."

Sen. Mike Lee, R-Utah, also criticized Trump over his support for Saudi Crown Prince Mohammed bin Salman despite reports that a CIA assessment concluded that the Saudi ruler ordered the murder of journalist Jamal Khashoggi. Lee said that Trump's assessment is “inconsistent” with the intelligence he’s seen. "Intelligence I've seen suggests this was ordered by the crown prince," he said.

Lee says that Khashoggi’s murder and Trump’s response provides “an opportunity” for Congress to weigh in to the U.S.-backed Saudi role in Yemen that has created a worsening humanitarian disaster.

"I think Congress has to take some ownership of U.S. foreign policy, especially as it relates to our intervention in this war," Less said. "Our unconstitutional fighting of a civil war in Yemen that has never been declared by the U.S. Congress as a problem. And that’s on us."