US warplanes bombed a suspected guerrilla safehouse west of Baghdad on Friday, stepping up a hunt for Jordanian militant Abu Musab Zarqawi believed to be behind a series of deadly attacks in Iraq.‘‘Somewhere between 20 and 25 people were killed in today’s strike,’’ said a US-led coalition official, who declined to be named. It was not immediately clear who was among the dead.The US military said the house in Falluja was a ‘‘known Zarqawi network safehouse’’ and was destroyed in the daylight strike, the third on suspected Falluja safehouses this week. Falluja residents said the house, in the southeast of the city, was reduced to rubble. Washington, due to hand over to an interim Iraqi government on June 30, accuses Zarqawi of links to Al Qaeda and say he has masterminded a number of major attacks, as well as being responsible for the beheading of an American and a South Korean.Militants in Falluja issued a taped statement on Friday denying Zarqawi was holed up in the town.The attack occurred shortly before Iraqi Defence Minister Hazim Al-Shalaan warned guerrillas that Iraq’s security forces, backed by the US-led coalition, were determined to crush them. ‘‘Today is the day for the Iraqi people to say to these traitors that the time has come for a showdown and God willing that showdown will be big and victory will be for us, the people,’’ said Shalaan, flanked by the interior minister.Meanwhile, the Mehdi Army militia of radical Shi’ite cleric Moqtada Al-Sadr declared a unilateral ceasefire on Thursday in a Baghdad slum — its last holdout against US troops. Sadr, apparently keen to enter mainstream politics, has already withdrawn his forces from Najaf and Karbala. Amid the violence and questions about the justification for the Iraq war, most Americans now say the US-led invasion was a mistake, a new USA Today/CNN/Gallup opinion poll showed. Fifty-four per cent thought the invasion had been a mistake, compared with 41 per cent who held that view three weeks ago. —(Reuters)