EU foreign policy chief Javier Solana has urged the US to engage in direct negotiations with Iran over Tehran's nuclear programme and other issues.
Mr Solana and Mr Larijani met for the first time in months
Mr Solana said he was convinced Iran wanted to talk with Washington.
He was speaking following talks in Ankara earlier this week with Iran's nuclear envoy Ali Larijani.
The US accuses Iran of seeking to build nuclear weapons. Washington has refused to hold direct talks until Tehran halts its uranium enrichment.
Iran says its nuclear programme is entirely peaceful and is solely aimed at producing civilian nuclear power.
Speaking at a gathering of European and US foreign policy experts in Brussels, Mr Solana said: "I think that at this point in time to have also the United States open a channel of communication with Iran will be worth thinking about.
The aim of the talks is to agree conditions for formal negotiations
"To think that we are going to find a stabilisation of the wider Middle East without opening some channels of communications with Iran, I think we are going to commit a mistake," he said.
Mr Solana said that his recent talks with Mr Larijani had indicated that there was "some potential motion".
He said he hoped to exploit that at a further meeting with the Iranian envoy in about 10 days' time.
Mr Solana added that he will brief US Secretary of State Condoleezza Rice on his discussions on Sunday.
Commenting on Mr Solana's remarks, US assistant Secretary of State Daniel Fried, who attended the Brussels forum, said: "Our position at the moment is well-known... So we are stuck".
Mr Solana and Mr Larijani met in Turkey's capital for the first time since the UN-imposed sanctions on Iran in March for refusing to suspend uranium enrichment.
Iran will face further sanctions if it has not stopped enrichment by a new Council deadline of 24 May.