By Fredrik Dahl and Hashem Kalantari
Iran defiant ahead of meeting of world powers to be attended by US in shift of policy.
Iran's highest authority said on Wednesday his country would retain its disputed nuclear work, voicing defiance ahead of a meeting of world powers to be attended by the United States in a shift of policy.
The United States will send a senior envoy, Under Secretary of State William Burns, to a meeting in Geneva between Iran and the powers to discuss Tehran's response to an offer of incentives if it suspends enriching uranium.
Burns will join European Union foreign policy chief Javier Solana and envoys from China, Russia, France, Britain and Germany in Saturday's discussions with Iranian nuclear negotiator Saeed Jalili, a US official said in Washington.
The US government had said previously it would not be involved in pre-negotiations with the Islamic Republic unless it halts enrichment, which can have both civilian and military uses.
But Iran has refused to stop its most sensitive nuclear work, as demanded by the six powers before formal talks can begin on the package of economic and other benefits they have offered to Tehran.
"This [nuclear] achievement belongs to all the Iranian nation and no power would be able to deprive the Iranian nation of this technology and certain right," Supreme Leader Ayatollah Ali Khamenei said.
"In relation to negotiations...we have very clearly defined red lines," he said in a speech quoted by state radio.
Iranian officials have previously said uranium enrichment was a "red line" and would continue.
The United States and other powers suspect Iran is seeking to build nuclear bombs under the cover of a civilian programme.
Iran, the world's fourth-largest oil exporter, says its nuclear work is solely aimed at producing electricity.
The standoff has sparked speculation of a military confrontation with the United States or Israel and helped push up oil prices to record levels.
US leaders have not ruled out military options if diplomacy fails to resolve the nuclear dispute with Iran.
Israel, long assumed to have its own atomic arsenal, has vowed to prevent Iran from emerging as a nuclear-armed power. It staged an air force exercise in June that stoked speculation about a possible assault on Iranian nuclear sites.
Tension increased further last week after Iran test-fired missiles in the Gulf, including one it says could reach the Jewish state and US bases in the Middle East.
Iran has vowed to strike back at Tel Aviv, as well as US interests and shipping, if it is attacked.
"The hand that would attack the Islamic Republic of Iran will be cut off," Khamenei said.
Fears of conflict has helped to push oil prices to new record highs, although prices fell $6 on Tuesday to around $138 a barrel amid growing concerns about the US economy. (Reuters)