US forces carried out two air strikes in June against militants targeting American troops, including one against an Iranian-backed militia, a spokesman for the military mission said Tuesday.
The comments marked the first time the US military had acknowledged calling in air power recently against militants in Iraq, as American troops prepare to withdraw from the country by the end of the year under a security pact.
Confirmation of the air strikes underscored warnings from Defense Secretary Leon Panetta, who had vowed in a visit to Baghdad last month that American forces were ready to act unilaterally to hit back at insurgents with Iranian backing.
In one of the strikes, Iranian-backed fighters were staging a rocket attack on a US base in Basra near the city's airport, Brigadier General Jeffrey Buchanan, spokesman for the US military in Iraq, told reporters at the Pentagon.
"We had a team of Apaches (helicopters) up at the time. They identified the guy firing the rockets, they engaged and killed him," Buchanan said.
"That was unilateral action but it was also self-defense," he said at Pentagon Press Association luncheon.
The militants were believed to be part of the Promised Day Brigade, created by anti-US Shiite cleric Moqtada al-Sadr to fight American forces.
In the second air strike, US forces killed two militants who were spotted with a detonator wired to a roadside bomb on a route where US convoys were headed, he said.
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Asked why the US military had not divulged news of the air raids earlier, the general said: "We don't intentionally withhold things."
But he also suggested it was up to the Iraqi government as Baghdad now oversaw security operations with US forces playing a support role.
Buchanan spoke a day after 74 people were killed in an Iraq's bloodiest day in more than year, with attacks in more than a dozen cities blamed on Al-Qaeda.
But despite the bloodshed, he voiced confidence in Iraq's security forces and said that overall rates of violence had steadily declined over the past several years.
Even taking into account Monday's violence, he said Al-Qaeda in Iraq had been seriously "degraded" and no longer posed the threat it had three or years ago.
Iranian-backed militant groups, however, represented a more serious danger "because of the support they are getting on a daily basis from Iran," as well as links to Iraqi political parties, he said.
The Iranian Revolutionary Guards Corps Qods force is "providing direct support in terms of manning, equipping, provision of intelligence," he said.
Iraqi security forces were increasingly aware of the threat posed by the three main Iranian-backed groups and had successfully targeted some of the fighters in recent months, he said.
Iraq's leaders agreed this month to open talks with the United States over a possible military training mission to last beyond a projected year-end American withdrawal.
About 46,000 US troops remain in Iraq.