A solid majority of House Republicans urged the chamber on Wednesday to repeal the budget caps on defense that remain a major hurdle to President Trump's proposed military buildup.

The 140 lawmakers, headed by Rep. Mike Turner of Ohio and including members of the fiscally conservative House Freedom Caucus, signed a letter to House Speaker Paul Ryan asking that the chamber make good on the White House's requested repeal of the so-called sequester.

Trump has proposed a $603 billion defense budget in 2018 that would smash through the caps by $54 billion. It faces a dim future in Congress unless lawmakers can negotiate a deal to either temporarily raise or repeal the caps, which it passed into law in 2011.

"What this shows is that budget hawks and defense hawks are together and that the effects of sequestration are so devastating to national security that people see this needs to be taken care of immediately," Turner, an Armed Services subcommittee chairman, told the Washington Examiner.

Military leaders have issued stark warnings about the state of the military after living for five years with budgets that have been constrained by arbitrary caps. Troops are undertrained and ill-prepared to deploy to war and equipment such as aircraft are aging and lack needed spare parts.

The letter was also signed by House Armed Services Committee Chairman Rep. Mac Thornberry of Texas and Republican Study Committee Chairman Rep. Mark Walker of North Carolina.

But it also included Rep. Mark Meadows, chairman of the House Freedom Caucus, and other members of the conservative voting bloc that has pressed for decreases in federal spending and been seen as the main obstacle to repealing the spending limits in the past.

For now, the threat of across-the-board sequester cuts hang over both defense and non-defense spending for 2018. The Republicans are proposing to free only the military from the budget ax.

The Democratic leadership on the House Armed Services Committee did not immediately respond to the proposal, but the party is likely to push back against any budget plans that favor defense while cutting all other funding.

Still, the widespread Republican support was a positive sign for that side. Turner said it sent a message to House leadership that repeal is a "clear win."

Turner, who cobbled together the signatures, released the letter as the House wrapped up a vote on an omnibus spending bill to keep the military and federal government funded through September and as Congress prepared to shift its attention to the coming year's budget.

Trump is expected to release his full defense proposal later this month, providing details for the first time on what he vowed to be one of the greatest increases for the military in U.S. history.

"We must afford our president the ability to restore military readiness and provide him with the necessary tools to protect our interests at home and abroad," the lawmakers wrote in the letter to Ryan.