WASHINGTON, May 21: The Pentagon said on Friday that the latest US incursion into North Waziristan was a mistake and the result of a misunderstanding.

A defence department official told reporters here that the troops had crossed into the Pakistani territory 'inadvertently'.

Meanwhile, Pakistan's Ambassador to the United State, Ashraf Jehangir Qazi has said that US officials have assured Pakistan that this is not the US policy. Pakistan sought this assurance after a recent statement by the US ambassador in Kabul, who said that American troops would continue to cross into the Pakistani territory in pursuit of the Taliban and Al Qaeda militants.

"They assured us that those who speak of crossing into the Pakistani territory violate the understanding given to Pakistan. American troops will not enter Pakistan in search of militants," Mr Qazi told a briefing here on Thursday evening.

US and Afghan officials have repeatedly charged that Al Qaeda and Taliban fighters have launched attacks inside Afghanistan from Pakistan's tribal region.

US Secretary of State Colin Powell also pointed this out when he told reporters after a meeting with Foreign Minister Khurshid Kasuri here on Thursday that the remnants of Taliban and Al Qaeda continued to "drift back and forth" across the Pakistan-Afghanistan border.

Earlier on Friday, Director-General of the Inter-Services Public Relations Maj-Gen Shaukat Sultan told reporters in Islamabad that US troops entered a border village in North Waziristan on Thursday and searched several houses before moving back into Afghanistan.

"We have already lodged a protest with the United States," Maj-Gen Sultan said. He, however, rejected media reports that said US forces had fired mortars into Pakistan during the incursion.