Myers, chairman of the Joint Chiefs of Staff, said on PBS television that Monday's capture of Abu Abd al-Aziz, whom he called Zarqawi's "main leader in Baghdad", was a "pretty good success" and was a blow to the anti-US uprising in Iraq.
"Just yesterday on the battlefield, we picked up Zarqawi's main leader in Baghdad - they call him the amir of Baghdad - Abu Abd al-Aziz, and that's going to hurt that operation of Zarqawi's pretty significantly," Myers said in an interview with PBS.
But Myers also acknowledged that US-led troops in Iraq faced "a very dangerous insurgency" that is far from being on its death bed.
No 'death throes'
Myers, who is scheduled to retire in two months, appeared to counter recent remarks by Vice-President Dick Cheney, who said the Iraqi uprising was in its death throes.
"You never heard Dick Myers ever say the insurgency has been broken ... insurgencies take time to break; they're broken by the political process."
However, he believed the anti-American uprising had
"You never heard Dick Myers ever say the insurgency has been broken ... insurgencies take time to break; they're broken by the political process"
General Richard Myers,
Joint Chiefs of Staff chairman
peaked and that US-led forces were having "pretty good success against pieces of this".
A defence official, speaking on condition of anonymity, said US forces were involved in the operation that snared Abd al-Aziz, but was unable to say whether Iraqi government forces played a role.
Myers did not offer any other details on the arrest.
The US military had reported raiding a safe-house west
of Abu Ghraib prison late on Sunday and arresting two men
described as "targeted terrorists".
But the names of those detained have not been released and
military officials could not confirm if one of them was Abd al-Aziz.
In a letter posted on a website earlier on Tuesday, purported to be from al-Zarqawi, he made no mention of any military setbacks for his organisation, choosing instead to lash out at Iraqi Shia, who make up the majority in Iraq's new government, accusing them of being "loyal to the Crusaders".
The disclosure of the capture in a prime-time US television interview comes amid growing indications the war in Iraq was losing support among Americans.
A CNN/USA Today/Gallup opinion poll conducted over the weekend showed 53% of Americans believed the Iraq war, ostensibly launched to rid Iraq of weapons of mass destruction that have never been found, was not worth fighting.
And 54% said the war had made the US more exposed to "terrorist" attacks.