Pentagon chief Chuck Hagel departed Thursday on a six-day tour of South America but the US-led war against the Islamic State group in the Middle East will be looming over his trip.

Hagel set off for Colombia, Chile and Peru with the world's attention focused on a dramatic battle in northern Syria, where Kurdish fighters have been holding out against IS jihadists with the help of air strikes from US and coalition aircraft.

Hagel has spent much of the past week in talks at the White House and conferring with top commanders, tracking the American-led air campaign in Syria and Iraq as well as an unfolding crisis over the Ebola epidemic in West Africa.

The conflict in the Middle East will be competing for Hagel's attention during his second trip to Latin America as defense secretary.

After talks in Colombia and Chile, the Pentagon chief will head to Peru where he will attend a meeting of regional defense ministers, officials said.

In Colombia, Hagel will highlight Washington's continuing support for the government's counter-insurgency operations and its efforts to clinch a peace settlement with the Marxist FARC rebels, the Pentagon said.

Hagel was scheduled to visit a military base to see training for Colombian special forces and aviators, spokesman Rear Admiral John Kirby said Wednesday.

His visit comes after the head of the US military's Southern Command, General John Kelly, urged the FARC rebels to sign a peace accord to end the decades-long civil war, saying they should "take the deal."

"If they are listening, this one time in 50 years, be smart, take the deal," Kelly said at a Washington conference on Tuesday.

From Colombia, Hagel proceeds to Chile and then Peru, where he will attend a security conference with senior officials from across the region.

At the gathering, Hagel will call for cooperative action to tackle organized crime, narcotics trafficking and other problems facing the Americas, Kirby said.

With environmental security a major theme of the conference, Hagel will describe how the Pentagon has sought to plan for climate change and its effect on military installations, operations and training, according to Kirby.