Iran's supreme leader Ayatollah Ali Khamenei on Monday banned any direct talks with the United States, a week after Washington reimposed sanctions on Tehran that were lifted under a 2015 nuclear deal.
US President Donald Trump last month offered to negotiate a "more comprehensive" deal but Iran said it would not negotiate under the pressure of sanctions.
"I ban holding any talks with America ... America never remains loyal to its promises in talks ... just gives empty words ... and never retreats from its goals for talks," Mr Khamenei said in remarks reported by state TV.
The supreme leader reiterated Iran's stance on his official Twitter account in English.
"Recently, U.S. officials have been talking blatantly about us. Beside sanctions, they are talking about war and negotiations," he said.
"In this regard, let me say a few words to the people: THERE WILL BE NO WAR, NOR WILL WE NEGOTIATE WITH THE U.S."
Mr Khamenei's declaration came as Iran unveiled a new short-range ballistic missile developed under a weapons programme that has alarmed US allies in the region and was a factor in Mr Trump's decision to pull out of the nuclear pact.
The defence minister, Brig Gen Amir Hatami, said the Fateh Mobin missile was an "agile, radar-evading and tactical missile with pinpoint accuracy" that had been completely locally developed and successfully test-fired.
"We will not spare any effort to increase the missile capabilities of the country and we will certainly increase our missile power every day," Iran's Tasnim news agency quoted him as saying.
"Be sure that the greater the pressures and psychological warfare against the great nation of Iran, our will to enhance our defence power in all fields will increase," he said.
Mr Trump has called for a new nuclear deal that restricts Iran's missile capabilities and interference in the region. US and UN investigations have found that ballistic missiles launched at Saudi Arabia by rebels in Yemen originated in Iran.
Iran's arsenal is believed to contain missiles with ranges of up to 3,000 kilometres.
The 2015 deal between Iran and world powers was intended to prevent Iran from developing nuclear weapons, but did not directly place restrictions on its missile development.