Javier Solana's comments came ahead of a meeting with European Union foreign ministers in Brussels today and talks on Iran later this week in Vienna at the International Atomic Energy Agency (IAEA).
The IAEA is set to consider whether to refer Iran to the Security Council for possible sanctions over its nuclear program.
On 20 November, Iran's parliament approved a bill requiring the government to block IAEA inspections if Tehran is referred to the council.
Iran's Foreign Ministry also said Tehran will not allow the IAEA to visit a military site in Tehran unless it provides "concrete proof" to justify an inspection. That site was razed just before IAEA inspectors paid an initial visit in 2004.