Karachi, Pakistan– ? Pakistani police defused a large bomb less than five minutes before it was timed to detonate Monday outside the U.S. Consulate, averting a devastating terrorist attack two days before Secretary of State Colin Powell visits this country.

The close call came as President Gen. Pervez Musharraf, a top Washington ally, said a Libyan member of al-Qaida was behind two bombings he narrowly escaped in December. Musharraf vowed to purge Pakistan of hundreds of foreign terrorists.

It was not clear who was behind the thwarted attack on the consulate in Karachi — Pakistan’s largest city of 14 million people and scene of a wave of anti-Western bombings since the Sept. 11, 2001, attacks — but suspicions immediately focused on Islamic extremists blamed for previous blasts.

“The man or men who left this van near the U.S. Consulate building wanted to blow it up,” Pakistani Information Minister Sheikh Rashid Ahmed told The Associated Press in Islamabad.

The Pakistani government and U.S. Embassy said Powell, currently in India, would arrive Wednesday for a two-day visit in Pakistan as planned. Pakistani police, using footage from surveillance cameras at the consulate, said a man dressed in a traditional Pakistani tunic parked a van outside the heavily guarded consulate at 7:14 a.m., then fled in a following car after he was challenged by a paramilitary guard.

Inside the van, police bomb disposal experts found a plastic water tank containing about 200 gallons of a liquid explosive mix — including the combustible fertilizer chemical ammonium nitrate — attached to detonators and a timer.