WASHINGTON (Reuters) - U.S. President-elect Donald Trump said on Friday Mexico would repay the United States for his planned border wall, a day after news emerged that his transition team was exploring getting the Republican-led Congress to vote to approve the funding.

U.S. President-elect Donald Trump talks to members of the media at Mar-a-Lago estate in Palm Beach, Florida, U.S., December 21, 2016. REUTERS/Carlos Barria

Trump told the New York Times he would most likely seek repayment through renegotiation of the North American Free Trade Agreement, which groups the United States, Mexico and Canada.

Sean Spicer, a spokesman for Trump, said on Friday the incoming administration would need government funding to build the wall and that Trump said in October Mexico’s payment would be a reimbursement.

“The idea that we’re going through the appropriations process and figuring out how to pay for it shouldn’t be news,” he told a briefing, confirming earlier reports on the funding.

Trump’s promise to build a wall on the U.S.-Mexico border, and make Mexico pay for it, was a major campaign theme and helped energize his supporters. The suggestion has infuriated Mexican officials who have said they would never agree to pay for a wall.

Trump may face resistance in Congress to the idea of the United States paying for the wall. Some Republican lawmakers worry about the high cost and question whether it is the best way to solve the complex issue of illegal migration.

Some conservative groups have called for a crackdown on benefits and jobs available to illegal migrants, which they say are a magnet for migration.

Republican Representative Luke Messer told reporters on Friday he had proposed legislation to get Mexico to pay for the border wall by ending a child tax credit given to illegal immigrant parents, which he said cost $4.2 billion annually.

“If you close that loophole for two years, you could pay for the higher ticket cost,” Messer said, referring to one estimate that a wall could cost $10 billion.

CNN and other media organizations reported on Friday Trump’s transition team had signaled to congressional Republicans that he preferred to fund the wall through Congress as soon as April.

In response, Trump tweeted that the media was not reporting that Mexico would repay money spent to build the wall.

A ‘Pay for the Wall’ memo Trump’s team issued in early 2016 proposed pressuring Mexico by cutting off remittances from undocumented Mexicans in the United States. It proposed amending the Patriot Act, passed after the Sept. 11, 2001 attacks, to include wire transfers as accounts that could be frozen.

“It’s an easy decision for Mexico: make a one-time payment of $5-10 billion to ensure that $24 billion (in remittances) continues to flow into their country year after year,” the memo said. “We have the leverage, so Mexico will back down,” it said.

Mexican President Enrique Pena Nieto’s office declined to comment on Trump’s comments on Friday. In August, Pena Nieto told Trump Mexico would not pay for a border wall.

Representative Martha McSally, the Republican chair of the border and maritime security subcommittee, told Reuters a 2006 law known as the “Secure Fence Act” would give Trump the authority he needs to extend fencing or build a wall.

An internal report prepared by U.S. Customs and Border Protection estimates initial costs for expanding border fencing would cost over $11.3 billion.

Building a wall would be more costly.

Trump has signaled since being elected that he would be open to fencing rather than a wall in some areas.

If funding was tied to a government funding bill, lawmakers could be forced to approve it to avoid a government shutdown. House appropriators have no interest in threatening a shutdown, spokeswoman Jennifer Hing said.

“The (appropriations) committee has not received any request from the Trump team or GOP leadership on this issue. If and when a proposal is received, we will take a careful look at it,” she said.

The Mexican peso MXN=, which briefly weakened about 0.2 percent against the dollar following Trump's tweet, fell to record lows this week as Trump intensified criticism of businesses making goods in Mexico rather than in the United States.