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 Ash 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.
A US-led coalition began air strikes against IS positions in Iraq and Syria last year. President Barack Obama said the objective was to “degrade and ultimately destroy” IS.
Although President Obama has not committed ground forces to Iraq, the US has about 3,500 troops in the country who have been helping to train Iraqi forces and also have a limited combat role.
Russia started its own air strikes in Syria at the end of last month, saying it wants to help President Bashar al-Assad defeat IS and other extremists.
But Washington has strongly criticised the Russian campaign, arguing that it has been focused on rebel opposition fighters and that it will only fuel more extremism.