President Bush's choice to be the top U.S. military officer says he is "especially concerned" by what he calls the "increasingly hostile role" of Iran in the Middle East.

Admiral Michael Mullen spoke Tuesday about the threat of Iran and the situation in Iraq at a hearing of the Senate Armed Services Committee.

Admiral Mullen said he is deeply troubled by what he called Iran's nuclear ambitions.

On Iraq, Admiral Mullen said no amount of troops and no amount of time will be enough unless Iraq's different groups take steps toward national reconciliation.

However, he said the deployment of additional U.S. troops to Iraq has made the security situation better, but in his words, "not great."

The Senate must confirm President Bush's nomination of Admiral Mullen to be Chairman of the Joint Chiefs of Staff.

The United States has accused Iran of supplying weapons and training to Shi'ite insurgents in Iraq. Iran denies the charge and blames the violence in Iraq on the U.S. military presence in the country. Iran also denies U.S. charges that its nuclear program is to develop nuclear weapons.

Some information for this report was provided by AP.