London: US President George W Bush says the United States can help calm the "testy situation" along the border of Afghanistan and Pakistan.

But the president is not endorsing a threat by Afghanistan President Hamid Karzai to send Afghan troops into Pakistan to fight notorious Taliban leaders.

Speaking at a news conference in London, Bush says the mission for the United States remains to deny safe haven to extremists who want to kill innocent people. The president said, "That's the strategy of Afghanistan. It needs to be the strategy of Pakistan."

Relations between Pakistan and Afghanistan are strained over allegations that the Taliban and Al Qaida find sanctuary in Pakistan's border regions.

Bush said, "We can help calm the situation down."