WASHINGTON (AFP) -- US lawmakers on Wednesday expressed alarm at the rising number of dead and wounded US troops in Iraq, with some highlighting fears that US forces may be overextended.

"While our military did remarkable work in defeating two terrorist regimes in short order, events in Afghanistan and Iraq make it clear that we have a ways to go in both countries," said Duncan Hunter, chairman of the House of Representatives Armed Services Committee.

"The terrorist elements have been defeated, but they haven't been destroyed, " he said.

Hunter worried that US forces are stretched thin, with some troops now in Iraq for nearly one year, and with no end in sight to the US military commitment.

"Because we have long-term commitments in Europe and Asia and long-term requirements in Iraq and Afghanistan and don't know how long the global war on terror will last -- or for that matter, whether it will ever end -- we face a future security environment loaded with uncertainty," he said.

"We face uncertain risks associated with the possibility of having to react to a future contingency while the bulk of our forces are already committed elsewhere," Hunter added.

Representative Ike Skelton, ranking Democrat on the committee, said the unsettling number of US casualites calls for a review of how the US occupation of Iraq is being conducted.

Skelton highlighted how more Americans have been killed in Iraq since April 14 than throughout the past year that US troops have been chasing al-Qaeda and Taliban operatives in Afghanistan.

"This morning -- like most recent mornings -- we awoke to the news of another servicemember killed in Iraq," he said.

Skelton said there had been at "one dead American each day" since President George W. Bush declared the end of major combat on May 1.

"I've been arguing for careful postwar planning to secure Iraq," he said. "The realities to date do not indicate that the planning that occurred was sufficient."

Since May 1, 16 US troops have been killed by hostile fire, the latest a soldier who was shot at a Baghdad filling station. Another was wounded.

"Given the challenges we're facing, we need our allies and their troops more than ever. We must not let our failure to agree before the war become an argument for a failure to achieve peace now," Skelton said.

In testimony at the hearing, Deputy Defense Secretary Paul Wolfowitz said the 146,000 US military personnel in Iraq should not need to be supplemented.

"We are pleased that the number and capability of coalition forces pledged to contribute to those operations is growing," Wolfowitz said, adding that the United States needed and would get more help from other countries in coming months.

But he also counseled patience: "It is only seven weeks since President Bush announced the end of major combat operations, and let me emphasize that word 'major.'

"As we expected and planned for, smaller combat operations in Iraq continue, even as we work with Iraqis to establish stable and secure areas throughout Iraq," Wolfowitz said.

He said US troops in Iraq were fighting forces waging a "guerrilla war."

"We've made great progress in some areas of the country, but we continue to face an adaptive and determined enemy, which, while defeated on the conventional battlefield, is nonetheless intent on killing Americans and Iraqis and disrupting the establishment of order in Iraqi society and the process of building a new and free country," Wolfowitz said.