President George W. Bush said Monday that Washington can help calm the "testy situation" between Afghanistan and Pakistan, but refused to endorse Afghan President Hamid Karzai's threat to send troops across the border as a means to target terrorists.

Bush called for leaders of Afghanistan and Pakistan to hold talks and share intelligence as both confront notorious Taliban leaders.

"There's a lot of common ground," Bush said. "It's in no one's interest that extremists have a safe haven from which to operate. Obviously, it's a testy situation there."

Bush declined to answer when asked directly whether he supports Karzai's threat to send troops in Afghanistan. Karzai said Sunday that Afghanistan has a right to send troops into Pakistan because Taliban militants cross over from Pakistan to attack Afghan and foreign forces.

Bush said, though, that he understands Karzai's concerns.

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

Last week, U.S. aircraft dropped bombs along the Afghan-Pakistan border, an incident the Pakistan army said killed 11 of its paramilitary forces. The exchange only deepened the increasingly touchy relations among the U.S., Afghanistan and Pakistan.

Appearing together, Bush and British Prime Minister Gordon Brown traded compliments about each other and their commitments to two war zones, Afghanistan and Iraq. They also offered a united front on Iran, Zimbabwe, Myanmar and Darfur and expressed hopes for reaching a global trade pact.

On at least two matters, Brown came ready with news that Bush wanted to hear.

The prime minister said Britain will freeze assets of Iran's largest bank, in a further move to discourage the country from developing nuclear weapons. He said that Britain will work to convince Europe to follow suit. Halting Iran's nuclear ambitions has been a major thrust of Bush's trip to Europe.

Brown also announced that his government was sending more troops to increasingly violent Afghanistan, another priority for the U.S. president.

Brown called Bush "a true friend of Britain" and praised his "steadfastness and resoluteness." Bush said of Brown, "He's tough on terror and I appreciate it."

Questioned about Iraq, Bush said that history will judge how the U.S. waged the war — whether more troops should have been deployed and whether they should have been positioned differently. But he said he had no doubts about deposing Iraqi leader Saddam Hussein. "Absolutely it's necessary," the president said.

Brown showed no distance from Bush on the strategy in Iraq. The prime minister said he would not order an arbitrary withdrawal of the 4,000 remaining British troops until the task is done, even as his government was announcing that it would bolster its forces in Afghanistan to its highest level ever.

"The policy is showing success," Brown said of Iraq. "In Iraq, there is a job to be done and we will continue to do the job and there will be no artificial timetable."

Bush cast the British and U.S. approach to withdrawal in the same terms: "The plan is to bring them home based on success." He said: "I have no problem with how Gordon Brown is dealing with Iraq. He's been a good partner."

Defense Secretary Des Browne will outline Brown's plans to boost British forces in Afghanistan to lawmakers later Monday.

Brown's office said around 230 engineers, logistical staff and military trainers will be deployed within weeks.

Britain currently has about 7,300 soldiers based mainly in the volatile southern Afghan province of Helmand. Prince Harry, the third in line to the throne, served there for 10 weeks until March.

More than 100 British troops have died in Afghanistan since 2001 — almost all of them since 2006.