FILE - In this April 15, 2016, file photo, a Donald Trump supporter flexes his muscles with the words "Build The Wall" written on them as Trump speaks at a campaign rally in Plattsburgh, N.Y. Congressional Republicans and Donald Trump's transition team are exploring whether they can make good on Trump's promise of a wall on the U.S.-Mexico border without passing a new bill on the topic, officials said Thursday, Jan. 5. (AP Photo/Elise Amendola, File)
FILE - In this April 15, 2016, file photo, a Donald Trump supporter flexes his muscles with the words "Build The Wall" written on them as Trump speaks at a campaign rally in Plattsburgh, N.Y. Congressional Republicans and Donald Trump's transition team are exploring whether they can make good on Trump's promise of a wall on the U.S.-Mexico border without passing a new bill on the topic, officials said Thursday, Jan. 5. (AP Photo/Elise Amendola, File) Credit: ap — Elise Amendola

Washington — Republicans on Capitol Hill say they don’t need to wait for Mexico to make good on President-elect Donald Trump’s central campaign promise: building a southern border wall.

In fact, they are happy to underwrite the wall themselves, at a potential cost of many billions of dollars.

The GOP’s willingness to fund Trump’s border wall with taxpayer money could put the party’s deeply held desire to rein in government spending in conflict with its long-standing goal of cracking down on illegal immigration and toughening border security. Nonetheless, many Republicans do not see an inherent conflict.

“It would be a proposal that would cost billions of dollars to get done, but if it’s an appropriate priority for our country, it’s worth spending that kind of money,” said Rep. Luke Messer, R-Ind., chairman of the House Republican Policy Committee.

There is no reliable price tag on building a border wall, but Trump has estimated the cost at $8 billion. Recent congressional legislation pegged the number at $10 billion, and construction experts say it could be more than double that.

The wall is one part of a massive spending strategy at the core of Trump’s populist agenda. Trump has not provided extensive details on how he plans to follow through on vows such as overhauling the tax code, repealing and replacing the Affordable Care Act, and executing a sprawling infrastructure program. But each of those proposals carries an exorbitant price tag, and experts say that combined, they could add trillions of dollars to the deficit.

Experts at the nonpartisan Tax Policy Center estimate that Trump’s tax proposals alone could add as much as $7.2 trillion to the deficit in the coming decade. Even-more-conservative estimates, such as those produced by the right-leaning Tax Foundation, concluded that Trump’s tax proposals would create at least a $4.4 trillion budget hole.

The costs of rolling back the ACA are harder to predict. Repealing the entire law would increase deficits by more than $350 billion over a decade, according to a 2015 report from the Congressional Budget Office, which serves as an independent scorekeeper.

If Congress plans to mimic a 2015 attempt at repeal, the eventual legislation could reduce deficits by $282 billion. But lawmakers have yet to reveal a plan to replace the ACA with tax breaks and benefits that could more than offset any savings.

Under President Obama, Republicans decried new federal spending to stimulate the economy, expand health-care coverage and pursue other domestic priorities.

But so far, they seem to harbor no similar qualms about Trump’s platform.