"I think our steps were very prudent and we've put on hold the potential for attacks on Americans," the acting defense secretary said, as he prepared to brief lawmakers on the regional tensions.

"I'd say we're in a period where the threat remains high and our job is to make sure that there is no miscalculation by the Iranians," Shanahan added.

His comments come amid a war of words between Washington and Tehran as both sides accuse the other of dangerously ratcheting up tensions.

The Pentagon accelerated the deployment of an aircraft carrier strike group to the Gulf and dispatched B-52 bombers to the region May 7 after US intelligence reported Iranian "threats" to US and allied forces.

The nature of threat has remained vague, although it reportedly included sightings of missiles being loaded on Iranian dhows in the Gulf.

Several tankers in the Gulf, including two Saudis, were reportedly sabotaged as well.

Members of Congress, including some Republicans, have expressed skepticism about the intelligence, however, as well as worries about the potential for miscalculation.

"I really want to underscore the credibility of the intelligence," Shanahan said, adding that he would be giving lawmakers a more detailed briefing about it.

Asked later what he meant by putting the threat "on hold," Shanahan told reporters, "There haven't been any attacks on Americans. I would consider that a hold."

"That doesn't mean that the threats that we've previously identified have gone away," he said.

"Our prudent response, I think, has given the Iranians time to recalculate. I think our response was a measure of our will and our resolve that we will protect our people and our interests in the region."