John McCain and Barack Obama are turning their foreign policy focus toward the war in Afghanistan, as new poll results show Americans consider that battleground more critical to the overall war on terror than Iraq.

The presidential contenders gave back-to-back addresses Tuesday on national security and foreign policy. Obama restated his pledge to end the Iraq war by the summer of 2010, while McCain and his surrogates accused Obama of wanting to concede defeat.

But both candidates devoted much of their speeches to staking out their strategies for Afghanistan, where violence is on the rise.

Nine U.S. soldiers were killed and 14 injured in a militant attack Sunday -- the deadliest attack on the U.S. military there in three years.

Obama and McCain both said they would send more brigades to Afghanistan as troops are removed from Iraq -- but they differed over the details and over how they would pursue terrorists operating next door in Pakistan.

Offering fresh criticism of Afghanistan, McCain told reporters Tuesday that there is serious corruption in the Afghanistan government and that President Hamid Karzai has not been the leader he would have hoped.

"(Iraqi Prime Minister Nouri al) Maliki has proved to be a more effective leader. ... Karzai has not been effective. Karazi has not been the strong leader that we had hoped that he would be. He is a very fine man. He just not has had as strong leadership that we had hoped," McCain said.

During his address, McCain said the strategy of increasing troop levels in Iraq should be applied to Afghanistan.

He said three more brigades should be sent to the country. And he said the Afghan army should be doubled to about 160,000 troops, calling on foreign countries to help pay for the cost of the increase. Speaking later to reporters, McCain hedged on whether the additional troops could come from NATO instead of the United States.

"The status quo is not acceptable. Security in Afghanistan has deteriorated, and our enemies are on the offensive," he said.

McCain also proposed appointing a White House czar on the Afghanistan war.

Obama said he, too, would send at least two more brigades to Afghanistan, but said the Iraq war, which he called a distraction, has prevented the United States from making progress in the region.

"If another attack on our homeland comes, it will likely come from the same region where 9/11 was planned. And yet today, we have five times more troops in Iraq than Afghanistan," he said.

He said in the 18 months since the troop surge in Iraq began, "the situation in Afghanistan has deteriorated -- June was our highest casualty month of the war."

Obama is preparing to take his first-ever trip to Afghanistan and his first trip to Iraq since becoming a presidential candidate.

In the run-up to his journey, McCain and Obama have clashed sharply over Obama's stated plan to remove troops from Iraq within 16 months of taking office. McCain also accuses Obama of waffling on that pledge when he said two weeks ago he's willing to "refine" his policies.

But Afghanistan could emerge as the second front, not only in the war on terror but in the presidential debate on national security.

McCain said Tuesday there is a "vast difference" between Obama's plan and his plan, which he said includes more specifics.

And the two candidates break over how to approach Pakistan.

Obama said the U.S. must apply new pressure on Pakistan to act on terrorist activity within its borders. He said that the U.S. must make clear that it is prepared to take out high-level terrorist targets in Pakistan if the Pakistani government does nothing.

McCain said that's the wrong approach.

"In trying to sound tough, he has made it harder for the people whose support we most need to provide it. I won't bluster and I won't make idle threats. But understand this, when I am commander in chief, there will be nowhere the terrorists can run and nowhere they can hide," McCain said.

McCain said, as president, he would track down Usama bin Laden and bring him to justice.

Both campaign dispatched surrogates to argue their positions on Afghanistan, as a new ABC-Washington Post poll shows a majority of Americans think Afghanistan is more important to the larger terror-fighting effort than the Iraq war is.

The poll found that 51 percent believe the United States must win in Afghanistan for the war on terror to be a success. Sixty percent responded that the war on terror could be a success without winning the war in Iraq.

According to the survey, 51 percent believe the war in Afghanistan is unsuccessful, up from 24 percent in 2002. Forty-four percent say U.S. efforts in Afghanistan are successful, down from 70 percent, the poll shows.

According to the poll, Americans were virtually split over whether a withdrawal timetable in Iraq is appropriate.

A new CBS News/New York Times poll showed Americans' perception of Iraq improving a bit. According to a preview of the poll by CBS News, 45 percent say the Iraq war is going "somewhat" well, up 10 percentage points from last month.

But only 7 percent say the war is going very well, and 59 percent still think the U.S. should have stayed out of Iraq in the first place.

The Associated Press contributed to this report.