"The Islamic Republic of Iran, as a country that has the potential to produce nuclear fuel, is ready to offer (that) fuel to international markets," Kharazi told the official IRNA news agency at Tehran airport after a trip to Italy and the Vatican.
Iran has been accused by Washington of secretly developing nuclear arms, a charge Tehran denies.
Iran has said it will enrich uranium only to the level needed to fuel power stations and not to higher, weapons-grade purity.
Britain, France and Germany last year persuaded Iran to suspend uranium enrichment and accept snap inspections by the International Atomic Energy Agency (IAEA), a UN watchdog.
Iran insists its suspension of uranium enrichment is a temporary goodwill gesture.
Diplomats report Iranian failure to suspend all enrichment-related activities has annoyed France and Britain.
Washington this week upped pressure on Tehran after the IAEA discovered undeclared drawings of centrifuges that can be used to make bomb-grade material.
Cooperation with IAEA
The United States made clear on Friday it would give Iran more time to disclose its nuclear programmes before deciding whether to refer the issue to the UN Security Council, which could impose sanctions.
Western diplomats in Vienna said the drawings showed Tehran had not complied with a demand from the IAEA governing board that it should provide a full and truthful account of its entire nuclear programme.
But Kharazi pledged Iranian cooperation with the UN nuclear watchdog.
"The United States is following its own agenda as it did before and intends to put the agency and its governing council under new pressure," he said.
The IAEA board meets again on 8 March.