People look at destroyed tanks belonging to forces loyal to Libyan leader Muammar Gaddafi after an air strike by coalition forces, along a road between Benghazi and Ajdabiyah March 20, 2011. [Photo/Agencies]

WASHINGTON - Cruise missile attacks launched by the US military had "significantly degraded" Libya's air defense capability, Bill Gortney, director of the Joint Staff said on Sunday.

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Briefing reporters at a Pentagon news conference, Gortney said the United States, Britain and France are now enforcing the no-fly zone over Libya which, according to him, covers roughly one-third of the North African country's territory. But he said Libya may still be able to fly helicopters. He said the assaults have been effective.

Gortney said the coalition currently involved in the military actions against Libya includes the United States, Britain, France, Canada, Italy, Belgium and Qatar. He said no allied forces' planes have been lost in the attacks, and they all returned safely.

Gortney said Libyan leader Muammar Gaddafi is currently not on the target list of the military attacks, and the military has no evidence that the assault has harmed Libyan civilians.

After firing over 110 Tomahawk cruise missiles to knock out Libyan air defense systems Saturday, the United States dispatched war planes Sunday to join the bombing campaign conducted by French and British planes. Gortney said US Air Force dispatched three B-2 stealth bombers to attack an airfield Sunday. According to earlier report, the use of stealth bombers were intended to destroy Libyan Air Force planes.

In an interview, Michele Flournoy, undersecretary of defense for policy said "the first steps of establishing any no-fly zone are taking out the adversary's air defenses," and that's what the Tomahawk and B-2 attacks were all about. Gortney said the attacks targeted Libya's long-range SA-5 surface-to-air missile systems, early warning sites and key communication nodes.

In addition to the targeting air defense sites, other US war planes conducted a mission with British and French planes, attacking Libyan ground troops in an area about 10 miles south of rebel stronghold Benghazi.

Gortney said Libyan forces were under "significant stress... isolation and... confusion."

When asked how long the military operation will last, Gortney said right now it is too early to tell the timeline, and the US military was not ruling out additional attacks against Libyan air defense targets.

Flournoy also said the mission does not end with establishing the no-fly zone, but admitted directing coalition air power against Libyan tanks and armored vehicles in the cities will be difficult.