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 to threaten its neighbors.
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 administration had given a rough deadline of the end of 2009 for Iran to respond to an offer of engagement and show that it would allay world concerns about its nuclear program.
Mullen, chairman of the Joint Chiefs of Staff, supports that offer, and has said any military strike on Iran, whether by Israel or the United States, should be a last resort.
The U.S. and others worry that Iran's program is intended to develop nuclear weapons. 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.
Meanwhile, Iranian nuclear negotiator Saeed Jalili called Monday for the disarmament of all nations with atomic weapons, but said all countries have the right to develop nuclear energy.
"The crime that was committed in Hiroshima must never be repeated," he told reporters during a visit to Japan, referring to the bombing of Hiroshima at the end of World War II.
The Obama administration is now beginning a push to get international support for additional penalties against Iran for its leaders' refusal to verifiably prove peaceful intentions, and Mullen suggested he thinks 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.
"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."
The administration is concerned about Iran's refusal to carry through on a tentative deal struck in October that called for Iran to ship the majority of its low-enriched uranium out of the country in exchange for fuel to run a research reactor.
The deal was seen by the U.S. and its negotiating partners as a step toward building confidence in Iran's claim that its nuclear program is designed entirely to generate power, not weapons.
The administration also stepped up the momentum toward sanctions after the revelation in September that Iran was secretly building a second uranium-enrichment facility near the holy city of Qom.
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," Mullen 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."
Republican Sen. John McCain 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."