Iran's chief nuclear envoy warned the United States on Tuesday against climbing into "the boxing ring" over his country's refusal to freeze uranium enrichment, while signaling that Tehran wants to negotiate over fears that it may want to develop an atomic bomb.

Ali Larijani's comments came the same day Iran's President Mahmoud Ahmadinejad said his country was ready to stop its enrichment program and return to talks — as long as the U.S. and the rest of the West stopped their own enrichment activities.

However, Larijani's statement — issued on the eve of a U.N. Security Council deadline for Iran to stop enrichment or face tougher sanctions — still offered no hints that his country was ready to meet that demand.

"If they ... move into the boxing ring, they would have problems," Larijani told reporters in response to a question about U.S. pressure on Iran to give up enrichment. "But if they sit at the chess table, then both sides would come to a result."

With the U.S. recently more robust in accusing Iranians of helping insurgents in Iraq and in beefing up its naval presence in the Gulf, Larijani's comments were seen as veiled warnings that any U.S. pressure would be met in kind.

• Monitor the nuclear showdown in FOXNews.com's Iran Center.

"Anybody interested in ... irrational moves ... would definitely receive an appropriate response," he said.

While saying his country was prepared to deliver "assurances that there would be no deviation ... toward a nuclear weapons program," he offered no new suggestions — and indirectly ruled out the key international demand that Tehran suspend enrichment, saying that was just a "pretext" to put political pressure on his country.

Earlier, as he went into a meeting with Mohamed ElBaradei, the head of the International Atomic Energy Agency — the U.N. nuclear watchdog — Larijani said his country was "looking for ways and means to start negotiations."

Asked what Iran was seeking, Larijani replied: "Constructive dialogue that could ... address the concerns" both of Tehran and of the world powers fearing that Iran wanted to use enrichment to develop nuclear arms.

But — with no sign that Larijani was carrying new initiatives with him — his call for new negotiations was unlikely to be taken up by the other side — the United States, France, Britain, Russia, China and Germany — which broke off earlier talks over Tehran's refusal to mothball enrichment. They also were not expected to deflect the threat of more severe U.N. Security Council sanctions.

Tehran's refusal to freeze all its enrichment-related activities prompted the U.N. Security Council on Dec. 23 to impose sanctions targeting its nuclear and missile programs and persons involved in them. Back then, it gave the country 60 days to halt enrichment or face additional measures — a deadline that expires Wednesday.

Those sanctions could be triggered by a report from ElBaradei to his agency's 35 board member nations, expected Wednesday. That report is expected to say that Iran has expanded enrichment activities instead of freezing them.

Still no sanctions were expected immediately. The five permanent Security Council nations — the United States, Russia, China, France and Britain — were likely to mull further action and consult on a common approach before the council takes up the issue.

Ahmadinejad said earlier Tuesday that his country was ready to stop its enrichment program and return to talks — but attached a condition that the international community was unlikely to accept. He said Western nations also must stop their own enrichment activities.

"Justice demands that those who want to hold talks with us shut down their nuclear fuel cycle program too," Ahmadinejad told thousands of people in northern Iran. "Then, we can hold dialogue under a fair atmosphere."

Iran has rejected the Security Council resolution as "illegal," and said it would not give up its right under the Nuclear Nonproliferation Treaty to enrich uranium and produce nuclear fuel.

The United States and its allies suspect that Iran is using its nuclear program to produce an atomic weapon — charges Iran denies, saying its aim is to generate electricity.

Enriched to a low level, uranium is used to produce nuclear fuel, but further enrichment makes it suitable for use in building an atomic bomb.

Ahmadinejad said Iran would not give in to coercion, and warned the U.S. and its allies that they would fail to force it into giving up its nuclear program.

"If you want to speak from the position of power and make use of the oppressing leverage of some international institutions, you have to know the you will fail against the unity and resistance of the Iranian nation," he said.

Visit FOXNews.com's Iran Center for complete coverage.