Ukrainian Foreign Minister Anatoly Zlenko is to hold urgent talks in the United Nations, following allegations that Kiev approved the sale of advanced radar systems to Iraq.

We still need to get from the Ukraine some explanation for the evidence which is emerging at the moment

Nato Secretary-General George Robertson

Foreign Ministry spokesman Serhiy Borodenkov said Mr Zlenko had broken off a trip to the Dominican Republic to meet UN Secretary General Kofi Annan in New York.

He is also expected to meet the Chairman of the UN Security Council's Iraqi sanctions committee, Ole Peter Kolby.

The visits comes after Nato Secretary-General George Robertson said "very serious questions" needed to be answered about evidence emerging of the alleged deal.

Earlier, the United States announced it was suspending more than $50m in aid to Ukraine and launching a policy review of its relations with the country.

Zlenko was visiting the Dominican Republic

Presidential administration head Viktor Medvedchuk said the accusations were aimed at boosting opposition to Mr Kuchma.

The row comes as Kiev faces a deep internal crisis, with opposition supporters holding a second day of protests and making increasingly vocal calls for Mr Kuchma's resignation.

US concern

Ukrainian Economics Minister Oleksandr Shlapak dismissed the accusations and said his government did not understand the US decision.

His remarks were the first high-level response from Ukraine to an announcement by Washington that the US is reviewing its policies towards a country that has been in the top five recipients of US aid for more than a decade.

The move comes after US officials authenticated tape recordings, in which they say President Leonid Kuchma is heard approving the sale of Kolchuga early warning radar systems to Iraq.

President Kuchma was heard to approve the sale

Speaking on the eve of his departure to Washington as head of Ukraine's delegation to the IMF and the World Bank, Mr Shlapak said there was still no proof that Ukraine has illegally sold weapons systems to Iraq.

Although existing humanitarian aid projects will be unaffected, Washington's decision is an unambiguous gesture of concern, says BBC Russian regional analyst Steven Eke.

The evidence is a secretly-made audio recording by Mr Kuchma's former security officer Mykola Melnychenko, in which the president is apparently heard approving a scheme to smuggle four radars to Iraq via a Jordanian intermediary.

Transcripts of the conversation have been in the public domain for some months, and the State Department says its delayed reaction is due to time-consuming efforts to authenticate the recording.

The US State Department says it has indications that the Ukrainian radars may already be in Iraq.

Known as passive radars, they are reported to be able to locate all types of aircraft - including stealth aircraft - while themselves remaining virtually undetectable.