Talks between Saeed Jalili and Javier Solana in London will take place as the five permanent UN Security Council members and Germany decide on tougher sanctions against Tehran over its defiance to halt uranium enrichment, which could be used in nuclear weapons production.
The Islamic Republic insists it needs nuclear fuel to generate electricity, its right under the non-proliferation treaty.
"We feel optimistic [about the meeting], but a lot depends on the other side," Jalili, head of the Supreme National Security Council, said reiterating that Iran would not give up its rights in the nuclear sphere "under outside pressure."
Iran's deputy chief nuclear negotiator Javad Vaeedi said on Wednesday the agreement on the meeting had been reached in a telephone conversation with Robert Cooper, EU director of external relations.
Solana's press office has not confirmed the meeting so far.
The 35-nation Board of Governors of the International Atomic Energy Agency (IAEA), will consider on Thursday and Friday Iran's cooperativeness with the UN nuclear watchdog following a generally positive report earlier this month on Tehran's nuclear activities by the IAEA chief.
Iran is under two sets of UN sanctions imposed since December. The United States and its allies have pushed for tougher measures, but Russia and China have blocked the move.
