The U.S. government at the highest levels is sending out word that the world is watching Iran as it proceeds with its nuclear program.

"The Iranians just need to know that the free world is working together to send a very clear message: 'Don't develop a nuclear weapon,'" President Bush (search) told reporters after meeting with Polish President Aleksander Kwasniewski at the White House on Wednesday.

"The reason we're sending that message is that Iran with a nuclear weapon would be a very destabilizing force in the world," Bush said.

Bush's comments followed similar remarks Secretary of State Condoleezza Rice (search) gave during a news conference in Brussels and in an interview with FOX News.

Rice told FOX's James Rosen that France, Germany and Great Britain must speak more forcefully to Iran’s hard-line Islamic government, which is balking at full inspections of its nuclear sites.

“The Iranians need to hear that if they are unwilling to take the deal, really, that the Europeans are giving, if they're unwilling to live with verification measures, to sign the additional protocol, to allow the IAEA in completely, then the Security Council referral looms. I don't know that anyone has said that as clearly as they should to the Iranians,” Rice said.

Later, after visits with both old and new members of the expanding North Atlantic Treaty Organization, Rice said the United States remains in "close consultations" with its European allies on the issue. She said Iran cannot indefinitely delay accountability for a suspected nuclear weapons program, but said the United States has set "no deadline, no timeline" for Tehran to act.

But she warned Tehran that the United States would not accept foot-dragging by the government there as officials weigh various diplomatic overtures that European nations have made to resolve the nuclear question.

"I'm quite clear and I believe everybody is telling the Iranians that they are going to have to live up to their international obligations," Rice said during a news conference with NATO (search) officials. "It is obvious that if Iran cannot be brought to live up to its international obligations, in fact, the IAEA statute would indicate that Iran would have to be referred to the U.N. Security Council" for possible sanctions.

"I think the message is there," Rice continued. "The Iranians need to get that message," she said, adding that Tehran should know that "there are other steps" the international community can take.

Iranian leaders claim their uranium enrichment programs are for peaceful purposes, not to build nuclear weapons. But the country so far has resisted the prospect of spot inspections by the International Atomic Energy Agency (search).

Rice highlighted the role of France, Germany and Great Britain because the three European nations have held talks with Iran since November.

In the interview with FOX News, Rice again argued for the Iranians to be referred to the U.N. Security Council for action.

“They [Iranian officials] need to hear that the discussions that they're in with the Europeans are not going to be a kind of waystation where they're allowed to continue their activities, that there's going to be an end to this and that they're going to end up in the Security Council,” she said.

Rice spoke to FOX News after telling a French audience Tuesday that it was time for the United States and European nations to put aside their differences over the Iraq war.

French Foreign Minister Michel Barnier used a news conference with Rice Tuesday night in Paris to repeat that France and the other European participants are committed to letting the diplomacy run its course.

He said he had asked Rice for American "support and confidence."

Rice told reporters that Iran is already on notice that it must not use a civilian nuclear power program to hide a weapons project.

Earlier Tuesday, Rice said in a speech that NATO can be a bulwark for freedom without playing world enforcer.

"How NATO's role will evolve, I think, is still an open question, but we need to be open to new roles that NATO might play," she said.

Alliance officials said in advance of her trip to Belgium that Rice's NATO visit would focus on preparations for a visit by President Bush on Feb. 22, when he will hold a summit with leaders of the other 25 allied nations.

NATO Secretary-General Jaap de Hoop Scheffer wants the meetings to seal a new unity in the trans-Atlantic alliance following bitter divisions over the Iraq war.

The talks are also expected to review NATO's peacekeeping missions in Afghanistan and Kosovo and its efforts to train Iraq's military. De Hoop Scheffer said last month's elections in Iraq — which were widely applauded in Europe — should boost allied efforts to expand its training mission.

Alliance defense ministers were set to discuss expanding both the Afghan and Iraq missions at a long-scheduled meeting Wednesday and Thursday.

NATO has been struggling to persuade governments to commit extra troops to both Iraq and Afghanistan. In Iraq, the problem has been compounded by the refusal of France, Germany and other nations that opposed the U.S.-led war to send instructors.

NATO currently has about 100 troops in Iraq on the training mission.

Rice's first trip abroad as secretary of state concludes Thursday in Luxembourg. She has said that either she or her second-in-command will visit each of the NATO capitals early this year.

FOX News' James Rosen and The Associated Press contributed to this report.