WASHINGTON (Reuters) - The United States wants Afghan President Hamid Karzai to arrest and prosecute corrupt government officials and take other concrete measures to shore up his legitimacy, the top U.S. military officer said on Wednesday, suggesting such steps were key to a troop increase.

Afghanistan's President Hamid Karzai speaks during a news conference in Kabul November 3, 2009. REUTERS/Ahmad Masood

Washington believes a successful counterinsurgency strategy hinges on winning Afghan public support for the government in Kabul and sidelining the Taliban.

But Admiral Mike Mullen, chairman of the U.S. military’s Joint Chiefs of Staff, said the re-elected president’s legitimacy among the Afghan people was “at best, in question right now and, at worst, doesn’t exist.”

Describing Washington as “extremely concerned” both by rampant corruption and Karzai’s public standing, Mullen said a housecleaning was needed at all levels of government and should be spearheaded by the president.

Karzai emerged this week as the victor more than two months after a fraud-marred presidential election and a resurgent Taliban prompted a White House war strategy review.

“He’s got to take concrete steps to eliminate corruption,” Mullen said. “That means that you have to rid yourself of those who are corrupt, you have to actually arrest and prosecute them. You have to show those visible signs.

“If we don’t get a level of legitimacy and governance, then all the troops in the world aren’t going to make any difference,” Mullen told a conference in Washington.

After weeks of internal deliberations, President Barack Obama’s advisers appear to be moving toward a hybrid war strategy combining counterinsurgency with counterterrorism in Afghanistan that would entail a troop increase next year.

With an announcement still expected to be weeks away, the biggest question remaining is just how many more troops and trainers Obama will decide to deploy, officials say.

The leading options under consideration would add at least 10,000 to 15,000 troops. General Stanley McChrystal, commander of U.S. and NATO forces in Afghanistan, has recommended adding about 40,000 troops, on top of the 67,000 U.S. troops and 42,000 allied forces currently there.

LONG FIGHT AGAINST CORRUPTION

Defense Secretary Robert Gates, a strong advocate of continuing a counterinsurgency strategy, has made clear that a decision on sending more troops cannot be put on hold until questions about Afghan government legitimacy and corruption have been resolved.

“The legitimacy question, the competency question, is one that’s not going to be answered with the outcome of an election. It’s one that’s going to take weeks, months, if not years to solve,” said Pentagon press secretary Geoff Morrell.

Lengthy deployments in Iraq and Afghanistan have put an enormous strain on the U.S. military but Mullen said “right now I don’t see us getting near a tipping point.” The war in Afghanistan began in 2001 and the war in Iraq started in 2003.

Mullen acknowledged that the United States would have to bear the brunt of any sizable troop increase, saying, “I don’t think it’s very realistic to think NATO is going to add thousands and thousands of troops.

“But it’s not just about troops,” Mullen said, citing the need for more trainers to expand the Afghan police force and improve government ministries.

Obama had promised to incorporate war spending in the regular budget process but Mullen said he saw the need for a supplemental spending bill to fund the war.

Mullen said Karzai, who was assured of another term this month when his main rival dropped out of the run-off, should ensure good governance extended from Kabul to the provinces.

The United States and its allies want Karzai to make merit-based appointments in key ministries and not to reward cronies who supported him in the election.

Washington also wants him to establish an anti-corruption commission to investigate top officials as part of a pact in which he also would give greater authority to local and provincial leaders.

“There’s huge frustration” among the Afghan public that needs to be addressed by Karzai, Mullen said, adding: “It is really up to him.”