The U.S. ambassador to the United Nations says Iran's nuclear program should be a test case for the Security Council. But Chinese and Russian envoys remain reluctant to take up the issue.

As U.S. and European diplomatic pressure on Iran mounted Tuesday, Chinese and Russian diplomats suggested there may still be time for negotiations.

U.S. Ambassador to the United Nations John Bolton maintained the Security Council has clear authority in the Iran uranium enrichment case under the U.N. charter. He called it a classic threat to international peace and security. But, acknowledging the diverse views among Council members, Ambassador Bolton cautioned that there is no guarantee of success.

"There are no guarantees in the Security Council. This will be a test for the Council, and appropriately so, because the Iranian pursuit of nuclear weapons and ballistic missile delivery systems threatens their region and threatens the world as a whole," he said.

But he cautioned that the Council's role should remained secondary, in enforcing the authority of the International Atomic Energy Agency, known as the I.A.E.A.

"That's not to say in any way that the IAEA will be displaced. Quite the contrary. We think Security Council involvement brings the possibility of strengthening the hand of the IAEA in dealing with the Iranian nuclear weapons program," he said.

But while American and European diplomats spoke confidently of a Security Council referral, two powerful Council members urged that diplomacy be given another chance. China's U.N. Ambassador Wang Guangya said taking the issue to the Security Council might have negative consequences.

"To refer this issue to the Security council where the P-5 [permanent five Security Council members] are still divided, I believe that under the current circumstances, when all sides are still talking about the possibility of resuming the negotiations, so talk too much about the Security Council and about sanctions would be counterproductive," he said.

Diplomats noted that the British draft text proposing Security Council referral stops short of recommending sanctions against Iran. Speaking to VOA, Russia's U.N. Ambassador Andrey Denisov called talk of sanctions "inappropriate".

"So how can we speak about sanctions or not sanctions. It's too early. All the instruments should be used in order to try to calm down situation, and to settle the matter. If for example, Iran, maybe it looks like wishful thinking, but if Iran announces that it is keen to resume moratorium, which definitely should be the best solution, then all the talks abut sanctions would be absolutely senseless," he said.

But while Russia shares China's concerns that taking Iran to the Security Council, Moscow has in the past few days moved closer to western views. The U.S. ambassador to the I.A.E.A. Greg Shulte told VOA's Persian service Tuesday that U.S., European, Russian and Chinese envoys have recently discussed gradually increasing diplomatic pressure on Tehran if it fails to suspend its uranium enrichment activities.

Ambassador Shulte said he is "fairly confident" the agency's board will report Iran to the Council at its February second meeting.