The top US military commander has reassured Persian Gulf nations of Washington's support in the face of regional concerns about Iran.
Speaking in Bahrain, Adm Mike Mullen said Tehran was a threat to peace but that the US "takes very seriously our security commitments in the Gulf region", AP news agency reported.
Gulf leaders have expressed fear over Iran's nuclear programme, which the US says is aimed at making a nuclear bomb.
Iran says its intentions are peaceful.
Adm Mullen held talks with the king of Bahrain, which hosts a large US naval base and lies across the gulf from Iran.
The US was "very ready" to meet any challenge from Iran, he said. "There are real threats to peace and stability here, and we've made no secrets of our concerns about Iran".
Iran has consistently denied that its nuclear programme is geared towards weapons, but was recently subjected to a fourth round of UN sanctions aimed at curtailing its nuclear activities.
However, Adm Mullen expressed fear that Iran was not being deterred. BBC News
