WASHINGTON (CNN) -- Attacks on U.S. and NATO troops in Afghanistan and support for the Taliban are both on the rise, but Iraq remains a bigger priority for American commanders, the chairman of the Joint Chiefs of Staff said Tuesday.
"In Afghanistan, we do what we can," Adm. Mike Mullen told the House Armed Services Committee. "In Iraq, we do what we must."
The southern Afghan province of Helmand -- the scene of recent heavy fighting between a resurgent Taliban and allied troops -- has seen a 60 percent increase in attacks in the past year, Mullen said.
Afghan troops backed by NATO forces recaptured the provincial town of Musa Qala from Taliban control Tuesday, allied commanders reported, but Mullen said polls show support for the Taliban in the country's southwest has risen to 23 percent -- "triple what it was just three years ago."
The Taliban has lost "a significant number" of leaders in recent months and have reverted to "terror attacks, thuggery and intimidation" as a result, he said.
U.S. troops have spent more than six years battling the Taliban -- the Islamic militia that once ruled most of Afghanistan -- and its al Qaeda allies in the original front in the "war on terrorism" launched by al Qaeda's September 11, 2001, attacks on New York and Washington.
Some members of the committee suggested more troops may be needed in Afghanistan.
Rep. Joe Sestak, a freshman Pennsylvania Democrat and a retired admiral, questioned the emphasis on fighting al Qaeda in Iraq when Taliban activity is up and al Qaeda has carved out new havens across the Pakistani border.
"I understand there's al Qaeda in Iraq, but our intelligence community tells us they don't plan attacks against the U.S. homeland," Sestak said. It is "those al Qaeda that live in either Pakistan or Afghanistan," that are a danger to the U.S. homeland, said Sestak.
But Mullen told the committee that the Afghan front "is by design and necessity an economy-of-force operation."
"Our main focus, militarily, in the region and in the world right now is rightly and firmly in Iraq," he said. "That is not to say the brave men and women in harm's way in Afghanistan -- American, coalition, Afghan -- are not valued or supported or in any way less important. It is simply a matter of resources, of capacity."
About 26,000 U.S. troops and more than 20,000 from NATO allies and other countries are currently in Afghanistan, Defense Secretary Robert Gates said.
Gates, who just returned from a trip to Afghanistan, has pressed the European allies to bolster their contributions of troops and helicopters to the theater and called for a new reconstruction effort led by "a strong civilian representative."
"The Taliban and their former guests, al Qaeda, do not have the ability to reimpose their rule," he told the committee. "But only in a truly secure environment can reconstruction projects take root and rule of law be consolidated. That environment has not yet been fully achieved, but we are working toward it."
Gates said examples of progress can be seen in towns like Khost, in southeastern Afghanistan near the Pakistani frontier.
Once "a hotbed of lawlessness and insurgent activity," he said, Afghan officials have worked with a U.S.-led provincial reconstruction team to promote economic development and security.
And Gates said the number of additional troops he wants from the allies is well below 10,000, including about 3,500 trainers for Afghan troops and police and about 20 helicopters.
"The numbers are not that big, which, frankly, is one of the sources of frustration for me in terms of our allies not being able to step up to the plate and meet these needs," he said. E-mail to a friend
CNN Pentagon Correspondent Barbara Starr contributed to this report.