By Phil Stewart and David Alexander

The United States called for a "greater commitment" from Iraq's government on Wednesday in the fight against Islamic State as it lamented Baghdad's failure to deliver enough soldiers for training and underscored the need to empower Sunni tribesmen.

U.S. Defense Secretary Ash Carter told a congressional hearing that the U.S. military had hoped to train 24,000 Iraqi security forces by this fall but had only received enough recruits to train about 9,000 so far.

"We simply haven't received enough recruits," Carter said.

"While the United States is open to supporting Iraq more than we already are, we must see a greater commitment from all parts of the Iraqi government."

President Barack Obama has faced mounting pressure to do more to blunt the momentum of the Sunni insurgents after they seized the provincial capital Ramadi last month, expanding their control over predominantly Sunni areas of Iraq.

The onslaught further exposed the shortcomings of Iraq's mainly Shi'ite forces and raised questions about the ability of the Shi'ite-led government in Baghdad to overcome the sectarian divide that has helped fuel the Islamic State's expansion.

General Martin Dempsey, the top U.S. military officer, said he would not recommend regularly deploying small numbers of American ground forces on the front lines, simply to stiffen the spines of the Iraqis, as some of Obama's critics have suggested.

"If their spine is not stiffened by the threat of ISIL and their way of life, nothing we do will stiffen their spine," Dempsey said, without ruling out short-term deployments to bolster a specific campaign, say to retake a major city.

Some lawmakers at the hearing questioned whether U.S. efforts to forge a unified, multisectarian Iraq were doomed.

"I fear that strategy won't work," said Adam Smith, the top Democrat on the House Armed Services Committee.

The Republican chairman of the committee, Mac Thornberry, cited Obama's critics, who say the strategy seems to be one of "retrenchment and accommodation" in the Middle East.

The United States sees training Sunni fighters, who would be subordinate to Baghdad, as crucial to the overall strategy. That goal in part led Obama last week to order 450 more U.S. troops to set up a new base closer to Ramadi.

Baghdad has routinely criticized the United States for failing to deliver weapons fast enough, and Reuters previously reported that the United States only recently started fielding weapons from a $1.6 billion fund approved by Congress last year.

(Reporting by Phil Stewart and David Alexander; Editing by Bill Trott and Tom Brown)

Reuters