The "gang of four is Cuba, Venezuela, Syria and Belarus. I don’t think there is any other country supporting Iran," said Nicholas Burns, the US State Department’s under secretary for political affairs.
"Iran seems to be determined to further isolation," he said.
But Burns said a diplomatic resolution could overcome the impasse between global powers and Tehran over its alleged ambitions to develop nuclear weapons, which Iran denies.
A June 2006 offer of cooperation and a suspension of sanctions in return for Tehran’s suspension of uranium fuel enrichment is still viable, he said.
"The offer is still on the table for us to negotiate," said Burns, at the end of a 24-hour visit to Argentina, which has its own concerns with Tehran.
"There is a way out, a diplomatic path forward, a diplomatic solution to this problem," Burns said.
"Iran is digging a hole deeper and deeper," Burns said.
The International Atomic Energy Agency, the UN atomic watchdog, has halted almost half its aid to Iran as part of UN sanctions, an IAEA report said Friday.
The UN Security Council on December 23 imposed sanctions on Iran for continuing to enrich uranium and called for cuts in the IAEA’s aid to the Iranian nuclear program.
Tension is escalating over Iran’s uranium enrichment, which United States says Tehran wants to build atomic weapons, while Iran says it wants to generate electricity.
Argentina has demanded Iran turn over former officials, including one-time president Akbar Hashemi Rafsanjani, it claims were involved in the 1994 bombing of a Jewish charity in Buenos Aires, in which 85 died.