Iran could carry out "provocative actions" in the Strait of Hormuz and elsewhere in that region in the future despite a period of relative calm, acting US Navy Secretary Thomas Modly said on Friday.
Tensions in the Gulf have mounted since attacks on oil tankers this summer, including off the coast of the UAE, and a major strike on oil facilities in Saudi Arabia. Washington has blamed Iran, which has denied being behind the attacks.
"I think they're going to continue to perform provocative actions over there... and I think they'll look at every opportunity they can to do that," Mr Modly told Reuters, without giving a timeline or details.
"There's nothing that suggests to me, short of a regime change there, that you have a different tone set from the leadership, that would suggest to me that they're going to stop doing what they've been doing," he added.
Since May, the Pentagon has sent 14,000 additional troops to the region to deter Iran, including an aircraft carrier.
Mr Modly suggested that US reactions to Iranian actions could take away from the Pentagon's focus toward priorities like countering China.
"As they start creating mischief over there... our reaction is we send an aircraft carrier over there for 10 months," he said.
"What does that do to our carrier readiness? It degrades readiness the longer it's over there."
His comments came as Iran's navy on Friday kicked off the first joint naval drill with Russia and China in the northern part of the Indian Ocean, Iranian state TV reported.
The four-day exercise, launched from the southeastern port city of Chabahar in the Gulf of Oman and near the border with Pakistan, is aimed at boosting security of the region's waterways, the report quoted Iran's navy chief Admiral Hossein Khanzadi as saying.
On Thursday, Chinese Defense Ministry spokesman Wu Qian said the drill would "deepen exchange and cooperation between the navies of the three countries." He said Chinese navy's guided missile destroyer "Xining" was taking part in the exercise.
Tehran has been seeking to step up military cooperation with Beijing and Moscow amid unprecedented economic sanctions from Washington. Visits to Iran by Russian and Chinese naval representatives have also increased in recent years.
The Iranian TV also said the drill shows that Iran is not isolated, despite the U.S. withdrawal from the 2015 nuclear deal with world powers and the Trump administration's escalated sanctions on Iran.
The drill is also seen as a response to recent U.S. maneuvers with its regional ally Saudi Arabia, in which China also participated.
