US Vice President JD Vance has said Iran must make a "meaningful" reduction in its nuclear enrichment capacity to satisfy American demands and end the seven-month war.

In an exclusive interview with Reuters in Fairbanks, Alaska, Vance said any deal would require Iran to cut enrichment capacity rather than offer promises of future drawdowns.

"If you don't want a nuclear weapon, then why do you need 60 per cent enriched fuel?" Vance said. "That's a very basic threshold issue."

Vance, who has led US efforts to negotiate a settlement, said Washington remained open to a deal but needed concrete concessions. "We're not going to trade words for actions," he said.

Iran's Foreign Ministry said the problem was "mixed messaging from US officials".

The two sides have exchanged proposals in recent weeks aimed at ending the war and reopening the Strait of Hormuz. President Donald Trump rejected Tehran's latest offer and warned military operations could intensify after the November midterm elections.

The war has jolted global energy markets and become a political liability for Trump and fellow Republicans ahead of the midterms.