WASHINGTON -- Five of the Bay State’s congressional members joined 27 other Democrats on Monday in urging President Obama to veto a Pentagon spending bill that they say could limit the president’s options in reducing the country’s nuclear arsenal.

The House has already passed the $642.5 billion measure, the 2013 National Defense Authorization Act, and the Senate is considering its own version. The defense authorization act is routinely updated each year as a spending blueprint for the military, but could be especially contentious this year because of continued debate over $500 billion in automatic cuts over 10 years to military spending to help ease the country’s budget woes.

Representative Edward Markey, a Democrat from Malden and one of the leading advocates for controlling the proliferation of nuclear weapons, is leading the effort to secure a veto of the bill, if unchanged by the Senate.

The White House has already indicated its concerns on several provisions of the bill that would limit its ability to implement the New Strategic Arms Reduction Treaty, which was signed into law by the president in April 2010.

In addition to Markey, Representatives John Olver, Barney Frank, Michael Capuano, and James McGovern signed the letter.

“We are gravely concerned that the policies in the bill fail to address our 21st century security needs,” the lawmakers wrote. “At a time when the US has formally agreed to reduce its nuclear arsenal under the New START Treaty, and there is a growing consensus among defense experts and retired military officers that a far smaller nuclear force is required for an effective nuclear defense and deterrent, we must reduce our nuclear weapons arsenal.”

The treaty with Russia was generally opposed by Republicans. Markey and other Democrats accuse the GOP-led House of using the budget process to circumvent the objective of the treaty.

Markey, senior member of the Energy and Commerce Committee, has pushed the Pentagon to reduce its nuclear arsenal. In February, he sponsored a measure that would cut $100 billion over the next 10 years, including reducing the country’s fleet of nuclear submarines.