The Senate adopted an amendment to the fiscal 2012 defense authorization bill yesterday that would place a $400,000 cap on the annual salaries earned by government defense contractors.

The amendment, proposed by Sen. Barbara Boxer (D-Calif.) and backed by senators Chuck Grassley (R-Iowa) and Jay Rockefeller (D-W.Va.), applies to contractors whose salaries are paid by tax dollars. The limit equals the annual salary of the president.

“Taxpayers should not be on the hook for exorbitant government contractor salaries. This amendment ensures that no defense contractor will make more in taxpayer funds than the president of the United States, who is the commander-in-chief.”

The amendment was agreed to by unanimous consent along with 10 others as a vote on final passage for the National Defense Authorization Act neared. A vote was expected to take place last night or today.

The Senate voted to advance a $662 billion defense policy bill that lays out spending priorities on Wednesday. The amount in the bill is $27 billion less than Obama’s request and $43 billion less than the amount appropriated for fiscal 2011, Sen. Carl Levin (D-Mich.), the chairman of the Senate Armed Services Committee, said. The Pentagon’s actual budget will be determined by the appropriations committees in both chambers.

The long-delayed bill was expected to easily pass after clearing cloture with an 88-12 vote.

President Barack Obama has threatened to veto the bill over a controversial provision that requires al-Qaeda suspects captured abroad to remain in the custody of the military. Amendments seeking to modify that language were defeated.

The Pentagon is facing $450 billion in reduced spending over the next 10 years, a number that could more than double under a sequestration measure if Congress cannot agree to a budget plan for the next decade by January 2013. A 12-member bipartisan “super committee” of senators and representatives failed to agree to a 10-year plan to reduce federal spending by a Nov. 23 deadline.

The bill also contains an amendment seeking to curtail the influx of counterpart electronic parts into the defense supply chain after a SASC inquiry found fake parts–mostly from China–had ended up in military systems. The measure would bar defense firms charging the Pentagon for resolving problems associated with counterfeit parts. It would require larger contractors to create systems for detecting and avoiding the parts, and calls for reduced payments to companies that fail to do so, according to Levin’s office.

The amendment was sponsored by Levin and Sen. John McCain (R-Ariz.), the ranking member minority member on SASC. 

If the bill passes, it will have to be reconciled with a House version passed earlier this year.