美防长访问伊拉克，誓言击溃伊斯兰国

U.S. Defense Secretary Jim Mattis said Tuesday Islamic State's "days are numbered," while cautioning that defeating the militant group is not imminent.

Mattis spoke to reporters before flying to Baghdad for an unannounced visit, where he met with Iraqi Prime Minister Haider al-Abadi.

The two discussed security cooperation and U.S. support for Iraqi security forces, Abadi said in a tweet. The Pentagon chief says stabilizing Iraq is "not going to happen overnight." "It's going to be a heavy lift for them going forward," Mattis noted.

U.S. forces have been leading a coalition of countries conducting airstrikes and other military operations in support of Iraq's military since August 2014, a few months after Islamic State fighters swept through large areas of northern and western Iraq. The Iraqi troops scored a major victory in July by recapturing control of Mosul, the nation's second largest city.

On Sunday, Iraq's military launched an offensive to take back Tal Afar, an area about 60 kilometers west of Mosul.

The U.S. coalition is also supporting efforts to expel Islamic State from areas it controls in neighboring Syria, including its de facto capital in the city of Raqqa.