Larson also confirmed that Iraq will be a "very, very significant topic" in the summit's agenda.

Bush is being accompanied by Secretary of State Colin Powell, National Security Adviser Condoleeza Rice and Secretary for Commerce Don Evans, when he arrives at Shannon airport on the west coast of Ireland on Friday.

The EU side includes Irish Prime Minister, Bertie Ahern, as the current president of the European Council, the outgoing Commission President Romano Prodi, EU High Representative Javier Solana and External Relations Commissioner Chris Patten.

In an interview with Eupolitix.com, Larson insisted that it was "very, very important" to have a united approach to Iran in ensuring compliance with the International Atomic Energy Agency's standards and said he was sure this would be discussed at the summit.

"We look forward to having a strong discussion of the proliferation challenges and will try to expand on the statement that we made last year on the importance of US-EU cooperation against proliferation of weapons of mass destruction," he said.

The Irish presidency has not specified that Iran would be on the agenda, but listed likely issues as the fight against international terrorism; the non-proliferation of Weapons of Mass Destruction; Iraq, Afghanistan, Sudan; the Middle East Peace Process and relations with the wider Mediterranean and Middle East.

With regard to Iraq, Larson said the US remained confident that, with the backing of the international community, an incoming interim government can take over from the US-led coalition on time.

"The handover will take place as scheduled, we think that the government is a strong one and will perform well, including in the area of security," he said.

The US under-secretary said that Washington believed "it is going to be important for the entire international community to give support to Iraq as it works to become a free, democratic and prosperous country."