Three House committee chairmen are calling on President Barack Obama’s administration to provide more information on defense budget cuts resulting from the new federal-deficit-trimming deal, raising concerns about the implications on national security under the largest-possible reductions.

House Armed Services Committee (HASC) Chairman Howard “Buck” McKeon (R-Calif.), House Appropriations Defense subcommittee (HAC-D) Chairman C.W. “Bill” Young (R-Fla.), and House Budget Committee Chairman Paul Ryan (R-Wis.) in an Aug. 10 letter expressed concerns about the prospect of $330 billion to $420 billion in defense budget reductions over the next decade under the first of two rounds of cutting.

“This would be an unprecedented drawdown in defense while U.S. forces are committed to contingency operations in Afghanistan and Libya, and possibly still in Iraq,” they wrote to White House Office of Management and Budget (OMB) Director Jack Lew and Defense Secretary Leon Panetta. They argued it is “more troubling” that Obama’s initial announcement of roughly $400 billion in such longterm cuts came in April before the Pentagon started its comprehensive roles and missions review, which is underway now.

The three lawmakers noted the Budget Control Act of 2011, which Obama signed Aug. 2, does not specify funding levels under a first round of cuts for the Pentagon and related defense agencies.

While the White House has said the measure reduces defense-related spending by $350 billion over 10 years, under the first of two rounds of cuts, the law itself only provides dollar caps for the initial two years. Also, those spending limits apply to the Pentagon, Department of Homeland Security, Department of Veterans Affairs, National Nuclear Security Administration, along with intelligence-community and international-affairs funding, and do not break down funding for each department or agency.

McKeon, Young, and Ryan are working to finalize the Pentagon budget for fiscal year 2012, which starts Oct. 1.

“Since we have not seen the outcome of the administration’s strategic review, it is imperative that members of Congress, and particularly members of our committees, obtain a better understanding of the impact of these reductions on the Defense Department and its ability to meet its mission,” they wrote to Lew and Panetta.

They asked for three things, including an update on the status of any preliminary conclusions from the comprehensive Pentagon review that could impact the budget, as they work on the FY ’12 defense bills.

They also requested information on any budget guidance OMB has issued to Pentagon for FY ‘13, because the three lawmakers said it may cite the largest possible defense cuts possible under the second phase of budget reductions.

McKeon, Young, and Ryan further asked Panetta and Lew to share more information on “the national security consequences” if up to $600 billion in defense cuts are added via a second round of reductions.

Under that second phase of federal budget cuts, according to the new law, a bipartisan Joint Select Committee on Deficit Reduction will attempt this year to find from $1.2 trillion to $1.5 trillion in additional overall federal spending over the next decade. If it and Congress can’t agree to a plan by the end of the year, $1.2 trillion automatically will be cut from 2013 to 2021 via a sequestration process, with half of those monies coming from a defense category defined as almost entirely the Pentagon. It is that sequestration trigger, and resulting defense cuts, the three House Republicans are concerned about.

Panetta, Lew, and Obama have all said they do not want the sequestration process to kick in. The hope is that the new 12-member committee, which will examine thorny issues including entitlement cuts and taxes, can agree to up to $1.5 trillion in overall federal savings.

House Minority Leader Nancy Pelosi (D-Calif.) named yesterday the three House Democrats that will serve on that Joint Select Committee on Deficit Reduction, rounding out the panel with lawmakers observers don’t expect to strongly protect defense spending.

She appointed Assistant Democratic Leader James Clyburn (D-S.C.), Democratic Caucus Vice Chair Xavier Becerra (D-Calif.), and Budget Committee Ranking Member Chris Van Hollen (D-Md.).

House Speaker John Boehner (R-Ohio) on Wednesday named conservative House Republican Conference Chairman Jeb Hensarling (R-Texas) as co-chair of the new Joint Select Committee. Boehner also named Reps. Dave Camp (R-Mich.) and Fred Upton (R-Mich.).

None of these six House members serves on the HASC or HAC-D.

Senate Majority Leader Harry Reid (D-Nev.) on Tuesday appointed Senate Democratic Conference Secretary Patty Murray (D-Wash.) as the other Joint Select Committee on Deficit Reduction co-chair to serve alongside Hensarling.

The other members named this week, by leaders of their party in their chamber, are Sens. Jon Kyl (R-Ariz.), Pat Toomey (R-Pa.), Rob Portman (R-Ohio), Max Baucus (D-Mont.), and John Kerry (D-Mass.).

Some of the senators have notable defense-industry leanings, including Murray, who is a member of the Senate Appropriations Defense subcommittee and noted defender of Boeing [BA] programs. Kyl, the Senate Minority Whip, has traditionally supported defense programs and has been outspoken on missile defense and nuclear matters. And Portman, a former director of Obama’s Office of Management and Budget (OMB), sits on the Senate Armed Services Committee.

Still, defense observers have generally been pessimistic about the chances of the 12-member panel protecting military spending.