TOKYO (Reuters) - UN Secretary-General Kofi Annan said on Thursday those involved in negotiations over Iran's nuclear crisis should tone down their rhetoric.

But Annan said he pinned his hopes on diplomatic efforts, including those by the European Union, to resolve the stand-off centering on Tehran's uranium enrichment program.

"There is also a need to lower the temperature, and refrain from actions and rhetoric that could further inflame the situation," Annan said in a speech to Tokyo university students.

Annan said Iran must "lift the cloud of suspicion" regarding its nuclear activities, but added that he hoped for a diplomatic solution rather than sanctions.

"It is my strong hope that the current discussions in the Security Council will give new momentum to the quest for a negotiated solution," he said.