The top U.S. military officer said Sunday he does not assume Iran's brief seizure of an Iraqi oil well is part of an orchestrated plan in Tehran.
Adm. Mike Mullen also said he's worried about "the clock now running" on the Obama administration's efforts at trying to keep the lines of communication open with Iran.
The chairman of the Joint Chiefs of Staff said "signals are very clearly in the air" about more international penalties against Iran over its nuclear program.
Special: Get Sarah Palin’s New Book – Incredible FREE Offer – Click Here Now.
The U.S. and others worry that Iran's program is intended to develop nuclear weapon. Iran says its work is peaceful and designed to generate electricity but has defied international demands to prove it is not trying to build an atomic bomb.
The administration is now beginning a push to get international support for additional penalties against Iran, and Mullen said he believed that backing was there.
"I think signals are very clearly in the air that another set of sanctions, another resolution, that that's coming," he said. He added that he favors President Barack Obama's outreach to Iran, and has said any military strike on Iran, whether by Israel or the United States, should be a last resort.
"I grow increasingly concerned that the Iranians have been non-responsive. I've said for a long time we don't need another conflict in that part of the world," he said. "I'm not predicting that would happen, but I think they've got to get to a position where they are a constructive force and not a destabilizing force."
Mullen, who spoke to reporters while flying from Germany back to the U.S., said the oil well incident adds to his concerns about Iran's intentions toward neighboring Iraq and the rest of the world.
"I worry a great deal about ... Iran and destabilizing as opposed to stabilizing," he said.
"And I worry about, you know, the clock now running on the dialogue and the engagement and sort of, where are we if that doesn't finish well? And certainly recent indications are ... they're not very responsive."
Meanwhile in Washington, senior Obama adviser David Axelrod said time was running out for Iran to cooperate.
"The international community is going to have to deal with that if they don't change their minds," he said. "I think that the world is united and is willing to take additional steps if the Iranians don't turn around. ... Plainly, there are going to be consequences if they don't turn around."
Sen. John McCain, R-Ariz., said the administration should act on its own to punish Iran and demonstrate support for Iranian dissidents.
"The president should stand up for the people who are demonstrating and risking their very lives on behalf of freedom on the streets of Tehran," he said. "Let's make it very clear we are with these people who are struggling for freedom as we always have."
Axelrod spoke on ABC's "This Week," while McCain appeared on "Fox News Sunday."
© Copyright 2015 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.