Senator Patty Murray of Washington will be co-chairwoman of a powerful new Congressional committee that is supposed to recommend at least $1.5 trillion of additional deficit-reduction measures, the Senate majority leader announced Tuesday.

The leader, Senator Harry Reid, Democrat of Nevada, appointed Mrs. Murray and two other Democratic senators — Max Baucus of Montana and John Kerry of Massachusetts — to the panel.

Mr. Baucus is chairman of the Finance Committee, which has authority over Medicare, Medicaid and taxes – – three prime areas of attention for the new 12-member panel, the Joint Select Committee on Deficit Reduction.

Mr. Kerry, the Democrats’ presidential nominee in 2004, is chairman of the Foreign Relations Committee.

Mrs. Murray, who won a tough re-election campaign last year, is a member of the Senate Democratic leadership, the Senate Appropriations Committee and the Bduget Committee. She is also chairwoman of the Committee on Veterans Affairs.

Her selection to lead the new panel raised eyebrows among some Republicans because she is also chairwoman of the Senate Democrats’ campaign arm, the Democratic Senatorial Campaign Committee.

In that role, Mrs. Murray recently assailed Republican candidates, saying they wanted to “end Medicare as we know it’’ and “turn it into a voucher program run by for-profit insurance companies in order to pay for more giveaways to oil companies and the very rich.’’

Senator Reid said that Mrs. Murray, a senator since 1993, had deep knowledge of budget issues and had shown an ability to “work across party lines.’’ That skill will be useful in the joint committee, which will be evenly divided between Democrats and Republicans, with a simple seven-vote majority needed to make recommendations.

“The world is watching the work of this committee,’’ Mr. Reid said.