George W. Bush’s efforts to shore up support for his military surge in Iraq suffered another blow on Monday when a senior Republican senator came out against the controversial plan.

John Warner, the former navy secretary and until last month chairman of the armed services committee, said he would introduce a resolution opposing the sending of 21,500 more US troops to Iraq. The resolution was also backed by two Republican senators, Susan Collins and Norm Coleman, and by Ben Nelson, a conservative Democrat.