John McCain yesterday accused his two Democratic presidential rivals of backing a dangerously reckless withdrawal from Iraq on the eve of politically charged testimony from General David Petraeus, the commander of US troops in Iraq.

General Petraeus faces questions on Capitol Hill today from all three presidential candidates – with Hillary Clinton and Barack Obama pledging to withdraw troops – knowing that the direction of US policy in Iraq hinges on who wins the presidential election in November.

Rarely has a battlefield commander given testimony before Congress at the height of such a contested and hard-fought presidential campaign. The Senate hearings will be as much about the posturing of the White House candidates as the progress report by General Petraeus.

Mr McCain was an early and vociferous advocate of the Iraq “surge” and is a staunch supporter of General Petraeus and his strategy of maintaining high troop levels.

Mr Obama and Mrs Clinton are, by contrast, battling for their party’s presidential nomination before a largely antiwar Democratic primary electorate. Both have pledged to withdraw US troops and to end the war. Mr Obama says that he would pull out all combat troops within 16 months. Mrs Clinton has been less specific but has promised to begin a withdrawal within 60 days of taking office.

In a speech to war veterans in Mis-souri, Mr McCain said that it was the responsibility of Mr Obama and Mrs Clinton to give an honest assessment to American voters of the “grave consequences of a hasty, reckless and irresponsible withdrawal”. He said that the US was “no longer staring into the abyss of defeat, and we can now look ahead to the the genuine prospect of success”. He said: “To promise a withdrawal of our forces from Iraq, regardless of the calamitous consequences to the Iraqi people, our most vital interests, and the future of the Middle East, is the height of irresponsibility. Doing the right thing in the heat of a political campaign is not always the easiest thing.”

General Petraeus will argue that the surge of 30,000 extra troops has resulted in impressive security gains in Iraq, but only modest political ones. He will recommend that troop levels should be reduced to the presurge total by the end of July, but will advocate a pause in any more reductions.

Mr McCain has a logistical advantage in today’s hearings. He is the senior Republican member of the Senate Armed Services Committee, with Mrs Clinton a junior Democratic member. He will thus speak before the former First Lady and he can interject. His aides say that he is likely to remind the hearing of Mrs Clinton’s statement to General Petraeus in September that it would take a “willing suspension of disbelief” to accept his upbeat predictions about the surge.

Mrs Clinton’s aides say that she will press General Petraeus and Ryan Crocker, the US Ambassador to Iraq, on the lack of political progress in Iraq, the rise of Iran, and the human and financial cost of the war.

Mr Obama will not get his turn in the limelight until much later, possibly not until after the evening news. He will be 13th to speak on the Senate Foreign Relations Committee, a hearing that does not begin until the afternoon. His aides say that he will focus on asking General Petraeus whether the Iraq war had made the US safer.

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