The US expects its operation against Iran to conclude within weeks, not months, and Washington can meet all its objectives without using ground troops, reported Reuters citing the US Secretary of State Marco Rubio on Friday.

Rubio ​told reporters after meeting G7 counterparts in France that Washington was "on or ahead of schedule in that operation, and expect to conclude it at the appropriate time here - a matter of weeks, not months."

Washington has dispatched two contingents of thousands of Marines to the region, the first of which is due to arrive around the end of March aboard a huge amphibious assault ship. The Pentagon is also expected to deploy thousands of elite airborne soldiers.

The deployments have raised concerns that the war, which the US and Israel launched on February 28 with airstrikes that killed Iran's supreme ​leader and other top officials, could turn into a prolonged ground battle.

While he said Washington could achieve its aims without ground troops, he acknowledged it was deploying some to the region "to give the president maximum optionality and maximum opportunity to adjust the contingencies, should they emerge."