The US has indicated a shift in its campaign against Islamic State (IS) militants in Iraq and Syria, including the use of direct ground raids.
Defence Secretary Ashton Carter said there would also be more air strikes against “high-value targets”.
Observers say his comments reflect acknowledgment of the lack of progress in defeating the militant group.
Separately, Iran says it is considering whether to attend international talks in Vienna this week on Syria’s war.
Earlier, the US said Iran – an ally of Syria’s President Bashar al-Assad – was being invited to the talks for the first time.