By Steve Holland

FORT DIX, N.J., Dec 15 (Reuters) - President Barack Obama used a holiday season visit to a U.S. military base on Monday to issue a tough warning to Islamic State militants, saying a U.S.-led coalition will permit no safe haven to the group and will destroy it eventually.

Obama spoke to hundreds of camouflage-wearing troops in a hangar at Fort Dix to thank the U.S. military for its actions around the world. In a display of bipartisan support for the troops, Obama was joined by New Jersey's Republican Governor Chris Christie, a potential candidate to succeed Obama in 2016.

The U.S.-led coalition in Syria and Iraq has had some successes against the Islamic State group but has yet to force a major rollback from the territorial gains the extremists made in seizing large swathes of Iraq last summer.

"Make no mistake. Our coalition isn't just going to degrade this barbaric terrorist organization. We're going to destroy it," Obama said.

Obama said gains are being made. Hundreds of vehicles and tanks and more than 1,000 fighting positions have been taken out, he said.

"We are hammering these terrorists," he said.

"They may think that they can chalk up some quick victories, but our reach is long. We do not give up. You threaten America, you will have no safe haven. We will find you and like petty tyrants and terrorists before you, the world is going to leave you behind and keep moving on without you, because we will get you," Obama said.

Obama also said the United States is on track to end its combat mission in Afghanistan at year's end, leaving behind a force dedicated to training Afghan security forces and carrying out counter-terrorism operations.

Obama last month approved a slight expansion in the U.S. role in the counter-terrorism operations. There are concerns in Afghanistan, however, about increasing Taliban attacks in the capital, Kabul.

Obama, who made ending the war in Afghanistan a priority, said challenges remain there.

"Afghanistan is still a dangerous place," he said. (Reporting by Steve Holland; Editing by Cynthia Osterman)