Solana will discuss the state of negotiations with Tehran on a trade and cooperation accord between Tehran and the European Union, which backs constructive engagement rather than the isolation policy favoured by the US.

The EU official will also travel to Israel, Jordan and Syria during the trip starting Friday and ending next Tuesday. In Israel he will meet Prime Minister Ariel Sharon and Foreign Minister Sylvan Shalom.

The Iran trip will come days before a decisive meeting of the International Atomic Energy Agency (IAEA), the UN's nuclear watchdog which is due to discuss the Iranian question from September 8-11.

Iran has come under increasing pressure, notably from the United States, to sign an additional protocol to the nuclear Non-Proliferation Treatyallowing snap inspections of its nuclear facilities.

Critics fear that Iran could be using its civilian nuclear activities as a cover to develop atomic weapons.

Concern over the issue resurfaced this week when a UN report said inspectors had found two types of highly-enriched nuclear particles at facilities in Iran not needed in civilian atomic programs.

The disclosure came after top US diplomat for arms control John Bolton left Moscow Tuesday reportedly empty-handed after failing to persuade Russia to stop its controversial nuclear cooperation with Iran.

Moscow's decision to continue helping Tehran build its first nuclear power plant at Bushehr is dogging US-Russian relations, though both Moscow and Tehran insist the facility has no military vocation.

The European Union last month expressed its "growing concern" about the nature of Iran's nuclear program and warned that, without credible guarantees, it would review its economic ties with Tehran in September.

Solana will underline that point during his trip to Tehran.

Negotiations on an EU-Iran trade deal are conditional on "the acceptance of the IAEA control monitoring system, cooperation with the fight against terrorism and the stabilization of the Middle East, as well as respecting human rights," his spokeswoman Cristina Gallach told AFP.

"They will discuss all the political questions linked to negotiations on concluding an accord between the EU and Iran. That means notably the nuclear issue and human rights," said another official.

Foreign Minister Kamal Kharazi said Thursday that Iran wants to cooperate fully with the International Atomic Energy Agency (IAEA), the UN's nuclear watchdog, but needs clarifications before signing the additional protocol.

Solana is also expected to discuss the broader questions of Iraq and the Middle East situation during the talks in Tehran, his spokesman said, adding that arrangements for whom Solana is to meet were not yet confirmed.

The EU official, due in Tehran Friday evening and Saturday, will then travel on to Israel where he will "repeat that there is no alternative to implementing the road map" agreed by the Quartet of the US, EU, Russia and the United Nations, said Gallach.

The trip will come as Israel steps up its lobbying of European governments to blacklist the political wing of the Islamic radical group Hamas, a step also called for by the United States.

Britain is leading a group of countries pressing for the move, which would freeze Hamas financial assets in Europe, while countries like France are against it, arguing that Hamas' political wing should not be marginalized.

EU foreign ministers are due to discuss the issue at an informal meeting next week in the Italian lakeside resort of Riva del Garda, although diplomats stress no decision is expected there.

Solana is likely to brief the EU ministers on his Middle East trip at the meeting, his spokeswoman said.

WAR.WIRE