"I think our steps were very prudent and we've put on hold the potential for attacks on Americans by Iran or its allies," Shanahan told reporters at the Pentagon on Tuesday. "And that's what's extremely important."
"I just hope Iran is listening. We're in the region to address many things but it is not to go to a war with Iran."
The administration sought to assure lawmakers in classified briefings that a war wasn't imminent. The briefings were the first for all members of Congress since the Trump administration more than two weeks ago declared a threat of an imminent Iranian attack and deployed several warships and bombers in the region.
But Shanahan, who addressed lawmakers alongside Secretary of State Mike Pompeo and Joint Chiefs of Staff Chairman Gen. Joseph Dunford, cautioned that threats by Tehran or Iranian-backed militias haven't been eradicated, the New York Post reported.
"There haven't been any attacks on Americans. I would consider that a hold," Shanahan said, adding that "doesn't mean that the threats that we've previously identified have gone away".
Some lawmakers pressed administration officials to be more open with the American public about potential threats of Iranian hostility and the US response.
"I think that would be helpful. I think one of the criticisms that was bipartisan was they didn't talk to us," said Senator Lindsey Graham after the classified briefing.
Senator Dan Sullivan said: "One of the things I mentioned in my remarks was that it would be useful, that some of this could be talked about more publicly, that would not reveal sources and methods."
Lawmakers were divided over whether the Trump administration was correctly interpreting the potential threat, with some saying the briefing emphasized the need for the military preparations.
American intelligence in early May suggested that Iran and its allies were planning attacks on US interests, prompting the deployment of US warships and bombers.
The Trump administration hasn't detailed the intelligence, although officials say that the military was concerned by indications that Iran or allied groups were transporting missiles on small boats and engaging in surveillance on American forces.
Iranian Foreign Minister Mohammad Javad Zarif, meanwhile, said on Tuesday that the US military was creating risks by crowding ships and aircraft into the region, although Iran doesn't intend to attack anyone.
Trump and his administration have provided shifting assessments of Iran's actions. Over the weekend, he warned that if there were a conflict, "that will be the official end of Iran".
On Monday, he said the US has no indication of hostile Iranian intentions.
( With inputs from IANS )