The Ukrainian President Leonid Kuchma continued to deny on Thursday that he had authorised arms sales to Iraq, and promised to co-operate with investigations into the affair.

His comments came in talks with the UK Defence Secretary, Geoff Hoon, who hinted Britain could consider taking action against the ex-Soviet state.

I am... concerned about the safety of our air crews operating over the no-fly zones in Iraq

Geoff Hoon

The US announced this week that it was suspending more than �50m of aid in protest, but Mr Hoon said he would not rush to judgement.

"I want to reflect upon the offer of co-operation that I have been given before any further decisions are taken by the United Kingdom Government," he said.

The European Union also said it would question Ukraine about the allegations of arms sales to Iraq, but was holding back from suspending aid.

Resignation calls

"Such a decision would have to be taken very carefully after assessment of all the facts available," the European Commission's external affairs spokesman told a news conference.

Zlenko was visiting the Dominican Republic

The sales, if confirmed, would constitute a violation of UN sanctions against Iraq, imposed after the 1991 Gulf War.

The US says it has examined and authenticated tapes of secretly recorded conversations between Mr Kuchma and the late head of the country's arms export agency, in which Mr Kuchma gives his consent to the sale of four Kolchuga radar systems to Iraq for $100m.

Mr Hoon said he was concerned for British air crews, along with US crews, policing two no-fly zones in northern and southern Iraq, set up after the Gulf War.

Mr Kuchma is also under intense pressure from domestic opposition parties, who have organised two major demonstrations in the last three weeks calling for him to resign.

Killings

On Thursday opposition leaders called on Washington to send all its evidence to parliament.

The opposition alleges that Mr Kuchma is guilty not only of agreeing to sell the radar systems to Iraq, but also of ordering the killing of the arms export agency chief, Valery Malev, whose voice is heard on the tape.

They also accuse him of ordering the killing of an opposition journalist, Georgiy Gongadze.

Ukrainian Foreign Minister Anatoly Zlenko has interrupted a trip to the Dominican Republic to fly to New York to rebut the US charges.

He is expected to discuss the issue with the president of the UN commission for sanctions against Iraq on Thursday.

He could also meet UN Secretary General Kofi Annan.

Nato Secretary-General George Robertson said on Wednesday "very serious questions" needed to be answered about the evidence emerging of the alleged deal.