The United States warned Saturday it was capable of deploying "overwhelming force" in the Middle East as it faced questions about its willingness to use its military power in the region.
Defense Secretary Lloyd Austin told the Manama Dialogue in Bahrain that all options would open if diplomacy fails to halt Iran's nuclear programme, but he was also forced to rebut claims the United States has become reluctant to use force.
The Pentagon chief was asked why Washington did not respond to last month's drone-and-artillery attack on a base used by the US-led coalition fighting the Islamic State group in Syria.
"The United States of America maintains the right to defend itself. And we will defend ourselves and our interests, no matter what, at the time and place of our choosing," he replied.
"And let no country, let no individual may be mistaken about that. We are committed to defending ourselves and our interests and that includes our partners as well," said Austin.
"And we're also committed to not allowing Iran to get a nuclear weapon."
Iran and world powers are set for talks later this month aimed at reviving an accord that placed restrictions on its nuclear programme in exchange for sanctions relief. The Islamic republic has always denied it wants seeking nuclear weapons.
Austin said the United States' major goal was to strengthen its "unmatched" alliances in the Middle East, but said military force remained an option with tens of thousands of its troops stationed in the region.
"America's commitment to security in the Middle East is strong and sure," he said.
After ending its 20-year occupation of Afghanistan in August, the United States is poised to withdraw its combat troops from Iraq by the end of the year.
Iran's Gulf neighbours are concerned that concessions could be made to the Islamic republic in the nuclear talks that are due to resume on November 29.
The United States and Israel, the sworn enemies of Iran, accuse it of using drones and missiles to attack American forces and Israeli-linked ships in the Gulf to destabilise the region.
This month, Iraq's Iraqi prime minister escaped an assassination attempt two days after security forces clashed with supporters of Iran-backed parties that lost support in recent elections.
On Saturday, Iran said it had seized a foreign boat smuggling diesel in the oil-rich Gulf.
Since February, Iran and Israel have been engaged in a "shadow war" in which vessels linked to each country have come under attack in waters around the Gulf.
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