WASHINGTON — Senate Armed Services Committee Chairman John McCain and his House counterpart, Rep. Mac Thornberry, are demanding Congressional budget negotiators support the $700 billion top line of their 2018 defense policy bill.

The call comes as congressional leaders and the White House move toward a two-year budget deal that would offer billions less. Congressional Quarterly reported Friday that negotiators are grappling with a GOP proposal to raise statutory spending caps for defense by $54 billion and nondefense funds by $37 billion in both fiscal 2018 and 2019.

Under that proposal, the cap would be $603 billion for defense, whereas the 2018 National Defense Authorization Act that passed the House and Senate this week authorized $626.4 billion in base defense spending, as well as $8 billion in defense funds authorized in other committees. This does not include roughly $65.7 billion in overseas contingency operations funds, which are exempt from budget caps.

McCain, R-Ariz., and Thornberry, R-Texas, argued that their bill was backed by large majorities when it passed in both chambers this week, though bipartisan votes. After conferees settled on a compromise between House and Senate versions of the bill, the House passed it 356-70 Tuesday, and the Senate passed it by voice vote Thursday.

“We believe that Congress has done its due diligence to authorize the appropriate level of funding based on threats, requirements, and missions,” they said in a joint statement.

They also argue Present Donald Trump “endorsed” defense spending at the $700 billion level. The administration, however, had requested $603 billion and later $4 billion for missile defense against North Korea.

As congressional negotiators work on a bipartisan compromise to fund the government when a stop-gap funding measure runs out at the end of the year, Democrats have reportedly balked at the GOP’s offer because it lacks parity for defense and nondefense increases.

McCain and Thornberry argue their process for drafting the bill included “months of deliberative bipartisan oversight, hearings, and negotiations. We expect that any budget agreement will reflect the hard work that Congress has just completed and the reality of today’s dangerous world.”

They also call on negotiators to set up further defense funding in fiscal 2019, a nod to the buildup promised by senior defense officials and Trump’s own rhetoric from his 2016 presidential campaign.

“We must not only set the conditions to pass an appropriations bill at the [fiscal 2018] NDAA level, we must also ensure the necessary growth in [fiscal 2019],” they said. “Without that, President Trump’s promise to rebuild our military will be impossible.”