Iran's Tasnim news agency reported on Friday that the country had unveiled a new ballistic missile with range of 2,000 km (1,200 miles), capable of carrying several warheads.
The report, which gave few other details, quoted the head of the Revolutionary Guards' aerospace division, Amirali Hajizadeh, speaking on the sidelines of a military parade in Tehran.
Hours earlier, President Hassan Rouhani vowed that Iran would boost its ballistic missile capabilities despite criticism from the United States and also France.
"Whether you like it or not, we are going to strengthen our military capabilities which are necessary for deterrence," Rouhani said in a speech marking the anniversary of the outbreak of Iran's devastating 1980-1988 war with Saddam Hussein's Iraq.
"We will strengthen not only our missiles but also our air, land and sea forces... When it comes to defending our country, we will ask nobody for their permission."
Criticism by the Donald Trump administration of a 2015 nuclear deal between Iran and major powers, including the United States, has focused heavily on Tehran's continuing missile programme.
Tehran says that the missiles are entirely legitimate under the terms of the deal as they are not designed to carry a nuclear warhead.
But Washington says they breach the spirit of the agreement as they have the potential to carry a nuclear warhead and has imposed new sanctions over Tehran's continuing launches and tests.
There has been some sympathy for the US position from France, whose President Emmanuel Macron said the deal could be expanded to ban missile tests and cut a sunset clause in the nuclear agreement that would see Iran resume some uranium enrichment from 2025.
But even he insisted that the core deal not be dumped.
Thus far, the UN nuclear watchdog and the US State Department have reported that Tehran has complied with the terms of the nuclear deal.
But Trump, who this week described the deal as an "embarrassment", is due to report to the US Congress on October 15 on whether or not he believes that Iran is in compliance.
If, as now appears increasingly likely, he decides that it is not, it could open the way for renewed US sanctions and perhaps the collapse of the agreement.
Trump said on Wednesday he had made his decision but was not yet ready to reveal it.
Washington has also taken aim at what it says is Tehran's failure to meet expectations that it would play a more stabilizing role in the Middle East.
"Regrettably, since the agreement was confirmed we have seen anything but a more peaceful, stable region and this is a real issue," Secretary of State Rex Tillerson told reporters at the United Nations.
Washington has been particularly concerned about Iran's heavy intervention in Syria on the side of the Assad regime and its support for Shiite rebels in Yemen who control the capital in defiance of its Saudi-backed government.
But Rouhani ruled out any change of policy in the region.
"Whether you like it or not, we are going to defend the oppressed peoples of Yemen, Palestine and Syria," he said.