The United States accuses Iran of secretly trying to develop nuclear weapons under cover of its civilian atomic energy programme, and wants the UN nuclear watchdog, the International Atomic Energy Agency, to take Iran before the UN Security Council. Tehran denies the charge.
"It would only make the issue more complicated and difficult to work out," Li said on Saturday during a news conference with Iranian Foreign Minister Kamal Kharazi.
"As far as I know, the Iranian government is having a very positive attitude in its cooperation with the IAEA," Li said, adding that he had told his colleagues "that China supports a solution in framework of the IAEA".
Li refused to speculate on whether China would use its veto in the Security Council in the event of Iran's case being sent there.
Russia, another permanent and veto-wielding Security Council
member, has also voiced its strong opposition to Iran's dossier
being referred there by the IAEA.
Meanwhile, Kharazi gave Iran's first formal reaction to George Bush's re-election, urging the US president to undergo a "change of behaviour" in his second term.
"This is an internal matter for the United States and the American people," Kharazi replied when asked to respond to Bush's re-election.
Bush put Iran into his 'axis of
evil' with Iraq and N Korea
"But what is important to us is a change of behaviour. In that respect, we hope for positive developments in the second part of Mr Bush's presidency," he said.
In 2002, Bush famously lumped Iran into an "axis of evil" along with Saddam Hussein's Iraq and North Korea.