"Given the leadership your country can provide and given the responsibility it has, it is important that it consistently and clearly indicate to countries like Iran that they must abide by their international commitments," Gregory Schulte, the United States' permanent representative to the International Atomic Energy Agency (IAEA), said in Pretoria.

Schulte was in South Africa at the invitation of the Center for International Political Studies at the University of Pretoria to speak about the controversy over Iran's nuclear activities.

South Africa started a nuclear-weapons program in the 1970s as a deterrent against neighboring states opposed to apartheid and Cold War instability that was fueling the war in nearby Angola. Two decades later, it voluntarily dismantled the program, winning praise from the IAEA.

Since then, the South African government had adopted a strict policy of disarmament and non-proliferation with regard to weapons of mass destruction and the capabilities to produce these weapons.

But South African media said this week that Pretoria's stance to support Iran's right to pursue peaceful nuclear technology had raised increasing concern in London and Washington.

The purpose of Gregory's visit to South Africa was to "try to get Pretoria to distance itself from Tehran," said a report in Business Day newspaper.

Iran has insisted that its nuclear program is for civilian purposes, but the United States fears Iran may be planning to make a nuclear bomb.

Schulte arrived in South Africa a day after Iran's Foreign Minister Manouchehr Mottaki met South African government officialsand said South Africa has an important role to play in resolving the dispute.

The UN Security Council, which has given Iran until the end of the month to stop its uranium enrichment program or face international sanctions, would consider an IAEA report next week on Iran's co-operation with the IAEA.

Iran responded this week to a package deal by the five permanent members of the UN Security Council and Germany by offering to discuss its nuclear program but not to suspend or give up enriching uranium.

"We need some indication that Iran is ready to negotiate seriously... we need an indication that it is not just playing for time," Schulte was quoted as saying by the SAPA news agency.

He added that suspension of the uranium enrichment was a key UN Security Council demand.

Schulte cited several countries that have a nuclear energy program without uranium enrichment.

"No one is denying Iran the peaceful use of nuclear energy," he said.

While the United States, Britain and France were pushing for sanctions if Iran does not comply with the UN demands, China and Russia said the country's offer this week should be discussed.

Schulte however said while it was hoped that a diplomatic solution could be found it was up to Iran to choose its future.

He was confident that should Iran not suspend its uranium enrichment program there would be support even from China and Russia for sanctions, but said these would be limited at first.

"Our goal is not to somehow punish the people of Iran. Our goal rather is to send a clear signal to the leadership that the path they are taking is not a constructive one," Schulte said.