UNITED NATIONS — Russia on Tuesday took its case to the United Nations Security Council that Ukraine is preparing to use a "dirty bomb", voicing its concerns during a closed-door meeting of the 15-member body.

Moscow sent a letter detailing the allegations to the UN on Monday, and Russia raised the issue at a closed meeting with the Security Council.

"We're quite satisfied because we had raised awareness," Russia's Deputy UN Ambassador Dmitry Polyanskiy told reporters. "I don't mind people saying that Russia is crying wolf if this doesn't happen because this is a terrible, terrible disaster that threatens potentially the whole of the Earth."

He said the evidence was in intelligence information that had been shared with Western counterparts with the "necessary level of clearance".

Kremlin spokesman Dmitry Peskov repeated Russia's allegations on Tuesday and said the West was foolish to dismiss them.

Ukraine dismissed Moscow's claim as an attempt to distract attention from the Kremlin's alleged plans to detonate a dirty bomb.

In a U-turn, a group of progressive Democrats in Congress said on Tuesday it had retracted a letter to the White House urging US President Joe Biden to engage in direct diplomatic talks with Russia, after it triggered an uproar among Democrats and raised questions about the strength of the party's support for Ukraine.

Representative Pramila Jayapal, chair of the Progressive Caucus, said in a statement that the caucus was withdrawing the letter it sent less than 24 hours prior. It was signed by 30 members of the party's liberal flank.

"The letter was drafted several months ago, but unfortunately was released by staff without vetting," the Washington Democrat wrote in a statement. Jayapal said she took responsibility for this as chair of the caucus.

The letter had called for Biden to pair the unprecedented economic and military support for Ukraine with a "proactive diplomatic push, redoubling efforts to seek a realistic framework for a cease-fire".

Several members of the Progressive Caucus issued statements expressing support for Ukraine, noting that they had joined other Democrats in voting for billions of dollars in aid for Ukraine.

Some said they had signed the letter months earlier and that things had changed. "Timing in diplomacy is everything. I signed this letter on June 30, but a lot has changed since then. I wouldn't sign it today," Representative Sara Jacobs said on Twitter.

On Tuesday, the Russian Foreign Ministry barred more persons from European Union member states from entering Russia in response to their anti-Russian actions.

Among the newly blacklisted are representatives of European manufacturers of weapons and military equipment supplied to Ukraine and some lawmakers of the Parliamentary Assembly of the Council of Europe, the ministry said in a statement.

It did not specify who is subject to the travel ban.

Agencies - Xinhua