Supreme Leader Ayatollah Ali Khamenei said on Wednesday Iran should further develop its military, including its missiles, after U.S. President Donald Trump made threats of force against Tehran if it refused to negotiate over its nuclear programme, Reuters reported.

Khamenei spoke a day after Iran’s U.N. ambassador Amir Saeid Iravani, condemned what he called “reckless and inflammatory statements” by Trump in interviews with the New York Post and Fox News in which he said he preferred doing a deal to prevent Tehran developing a nuclear weapon to bombing the country.

“Progress should not be stopped, we cannot be satisfied (with our current level). Say that we previously set a limit for the accuracy of our missiles, but we now feel this limit is no longer enough. We have to go forward,” Khamenei said, citing a need to focus on innovation in the Iranian military.

“Today, our defensive power is well-known, our enemies are afraid of this. This is very important for our country,” he added after visiting a Tehran exhibition showcasing the latest developments in Iran’s defence sector.

The semi-official Tasnim news agency said that during the exhibition a jet-powered “suicide drone” – loitering munitions that hover over targets – was unveiled with imagery of a submarine-launched kamikaze drone displayed for the first time, read the report.

Tehran insists its ballistic missile programme is purely defensive but it is seen in the West as a destabilising factor in a volatile, conflict-ridden region.

Khamenei, who said on Friday that talks with the United States were “not smart, wise or honourable”, made no mention of Trump in his remarks on Wednesday

Trump last week restored his “maximum pressure”, policy towards Iran that includes efforts to drive its oil exports down to zero to push the Islamic Republic into a deal that would severely constrain its disputed nuclear programme.

Western powers have long suspected that Iran’s uranium enrichment programme is a disguised project to develop nuclear bomb material. Iran denies this, saying it seeks nuclear energy only for peaceful purposes.

Iranian President Masoud Pezeshkian on Monday questioned U.S. sincerity in seeking talks with Tehran while imposing tougher sanctions echoing those Trump implemented during his first, 2017-21 term in office.

Iravani, Tehran’s United Nations ambassador, wrote in a letter to the U.N. Security Council that the Trump administration’s policy “reinforces unlawful, unilateral coercive measures and escalates hostility against Iran.”

Though Iran has long denied nuclear weapon ambitions, it is “dramatically” accelerating its enrichment of uranium to 60% fissile purity, close to the roughly 90% weapons-grade level, the U.N. nuclear watchdog chief told Reuters in December, Reuters reported.

Tehran has in recent months announced new additions to its conventional weaponry, such as its first drone carrier and an underground naval base amid rising tensions with the U.S. and its regional arch-enemy Israel.