"It's up to the six countries -- the five permanent members of the Security Council plus Germany -- to decide whether the time has come to follow the second track," Solana told reporters.

Solana made the remarks prior to the meeting of foreign ministers from Britain, China, France, Russia, the United States and Germany to discuss how to respond to Iran's refusal to suspend uranium enrichment.

The six countries had offered Iran a package including political, economic and nuclear technology incentives in return for Iran's suspension of uranium enrichment.

However, Iran defied a UN Security Council Aug. 31 deadline of suspending uranium enrichment-related activities.

The six countries have since followed a two-track approach: dialogue or referring Iran's nuclear case to the UN Security Council for possible sanctions.

"Despite numerous talks with Iran, we were not able to make an agreement on the key point: suspension (of uranium enrichment)," Solana have said after talks with Iran's chief nuclear negotiator Ali Larijani on several occasions.

He said the negotiations cannot last forever, but he also stressed that diplomacy was the only way to break the standoff.

"Iran's nuclear issue can only be solved and will be solved through negotiations," Solana said, adding that he didn't believe there was a solution through force.

The official also warned that referring Iran to the UN Security Council for possible sanctions could make further dialogue with Iran "impossible."

Iranian President Mahmoud Ahmadinejad reiterated on Thursday that Iranians have made their decision to achieve the "highest goals of scientific advancements and gain access to nuclear energy."

The United States accuses Iran of developing nuclear weapons under the cover of a civilian program, a charge that has been repeatedly denied by Tehran.

Iran insists that its program is aimed at generating power, to meet the country's surging energy demands.