The negotiations with Iran's top nuclear negotiator Saeed Jalili took place a day ahead of a meeting in Paris between the five permanent Security Council members and Germany, who are set to discuss tougher sanctions against Tehran over its refusal to halt uranium enrichment.
"I have to admit that after five hours of meetings I expected more. I am therefore disappointed," Solana told reporters, adding he would speak to Jalili again in December.
Jalili described the talks as "positive," but said Iran would not give in to international demands that it terminate uranium enrichment. The United States and its European allies fear the Iranian nuclear program could be used to build atomic weapons, while Tehran insists it will use enriched uranium for electricity only.
"Iran is a member of the Non-Proliferation Treaty, and this means it has the right to enrich uranium," Jalili, who heads the Islamic Republic's Supreme National Security Council, told reporters.
"Iran deems it unacceptable to give up its right to enrichment, while it is fulfilling its other obligations," he said.
The UN nuclear watchdog, the International Atomic Energy Agency, issued a generally positive report on Iran's nuclear ambitions earlier this month, saying the country has provided extra documentation, while noting that Tehran was continuing to enrich uranium.
The Islamic Republic is already under two sets of UN sanctions. The U.S., Britain, France, China, Russia and Germany are set to discuss tougher measures, including trade, financial and diplomatic restrictions.
However, the six nations have lacked unity on the issue. While Washington has pushed for tough punishment and even hinted at a military attack, Moscow and Beijing, who have substantial business interests in Iran, have so far blocked further sanctions.
Continuing Iran's uncompromising stance, Jalili said in London that Tehran would not halt nuclear research even if the UN Security Council imposes new sanctions: "If some countries want to use the UN Security Council and its resolutions to force Iran to drop research in the civilian nuclear sphere, they will clearly fail."
