Western governments have long suspected Iran of seeking to develop a nuclear weapons capability to counter widely suspected but undeclared arsenal of its arch-foe Israel.

"If the issue is nuclear weapons, yes, we too consider this type of weapon unacceptable," Araghchi, Iran's lead negotiator in the talks, said in a televised speech. "We agree with them on this issue."

Iran has held five rounds of talks with the United States in search of a new nuclear agreement to replace the deal with major powers President Donald Trump abandoned during his first term in 2018.

The two governments are at odds over Iran's uranium enrichment programme, which Washington has said must cease but which Tehran insists is its right under the nuclear Non-Proliferation Treaty.

Nonetheless, Trump said Wednesday that "we're having some very good talks with Iran", adding that he had warned Israeli Prime Minister Benjamin Netanyahu against striking its nuclear facilities as it would not be "appropriate right now".

Israel has repeatedly threatened military action, after pummelling Iranian air defences during two exchanges of fire last year.

Trump has not ruled out military action but said he wants space to make a deal first, and has also said that Israel, and not the United States, would take the lead in any such strikes.