Updated

President Obama is expected to extend the bombing campaign against ISIS in Libya for a second time, three U.S. military officials with knowledge of the request told Fox News.

The decision authorizes the U.S. military to launch a third month of airstrikes against ISIS in the Libyan coastal city of Sirte. Airstrikes began Aug. 1 following a request from the Uited Nations-backed government in Tripoli. At the time, the Pentagon said the Libya mission would likely last “weeks, not months.”

Extending the bombing campaign for another month in Libya means the Navy will have to keep two warships off the coast of Libya for up to a third consecutive month, according to defense officials. Drone strikes, which provide a majority of the strikes, would also be extended. The initial plan called for the two warships to remain off Libya for one month only.

One of the U.S. warships, the amphibious assault vessel USS Wasp, had been scheduled to go to the Persian Gulf in September to begin airstrikes against ISIS in Iraq and Syria, as well as keep an eye on Iran following recent incidents involving Iranian gunboats and U.S. Navy ships -- one of which resulted in warning shots being fired by a U.S. warship. The other, the destroyer USS Carney, was supposed to head to the Black Sea near Russia next month. But the Libya operation against ISIS has been deemed more pressing by senior military leaders.

U.S. Marine Corps Harrier jets and attack helicopters as well as drones have conducted 175 airstrikes against ISIS in Libya as of Monday, according to the U.S. military’s Africa Command, which is leading the operation.

The news comes as Obama approved the Pentagon’s request to deploy an additional 615 American soldiers to Iraq to help local forces prepare for the expected assault on Mosul, Iraq's second largest city.

Defense Secretary Ash Carter made the troop announcement Wednesday. The U.S. military is now conducting airstrikes against terror groups in six countries: Iraq, Syria, Libya, Afghanistan, Yemen and Somalia.

The USS Wasp is serving as the launch point for U.S. airstrikes in Libya. The USS Carney is serving as an escort ship and firing illumination rounds from its 5-inch gun to help a U.S.-backed Libyan ground force in Sirte, located roughly half way between Tripoli and Benghazi.

In addition to the airstrikes, U.S. special operations forces have been in and out of Libya for months advising local ground forces, according to defense officials.

When the Libya airstrikes began, a Pentagon spokesman said the strikes would only back ground forces associated with the fledgling United Nations-backed government known as the Government of National Accord (GNA) for a “finite” period of time and did not anticipate a long commitment.

“The duration of this operation will be measured based upon the length of time it takes for them to do that objective,” Capt. Jeff Davis said during a Pentagon briefing with reporters.

The mission will likely take “weeks not months,” Davis said at the start of the airstrikes in early August. “This is a finite period of time and a very finite mission ... We don’t envision this as being something that’s going to be too long,” he said.

Speaking at the White House in August, President Obama said supporting the Libyan government against ISIS was in “America's national security interests.”

ISIS fighters have been decimated in Libya since US airstrikes began, multiple officials tell Fox News.

Pentagon Press Secretary Peter Cook said in August the number of
ISIS fighters in Sirte was under 1,000. After nearly two months of a majority of drone strikes as well as U.S. Marine Corps airstrikes, the number of ISIS fighters in Sirte has been estimated to be “under 100,” according to a U.S. official with knowledge of the latest intelligence.

The official added that U,S, military operations in Libya could be ending soon. “It’s very close. ISIS is only in three neighborhoods [in Sirte],” the official added.

In June, CIA Director John Brennan said there were 5,000 to 8,000 ISIS fighters in Libya.