A new trilateral alliance between the United Kingdom, Poland and Ukraine may be announced as soon as this week, according to BBC sources.

Axar.az reports that the U.K. prime minister is expected to visit Kyiv on Tuesday, as is Polish leader Mateusz Morawiecki, with reports suggesting the pair could use the opportunity to announce the formation of the new alliance alongside their Ukrainian counterpart.

“We are seriously working on this option and talks are ongoing. We are ironing out the details,” a source in the Ukrainian president’s cabinet told the British broadcaster. The BBC explained that the main aim of the new alliance would be counteracting the Russian threat and common work for the future of European security. The new alliance is to be established against the background of the growing threat on Ukraine’s borders and the U.K.’s weapon deliveries to Kyiv.

Poland on Monday announced that it will supply Ukraine with weapons. The head of the President’s National Security Bureau Pawel Soloch told journalists that “a decision was made to supply the Ukrainian side with defensive munitions.”

British Foreign Secretary Liz Truss had initially outlined the potential for a British-Polish-Ukrainian alliance on Jan. 21. According to the BBC, Ukraine initiated the new cooperation format at the start of December and is meant to be part of the strategy of small alliances such as the Lublin Triangle formed between Poland, Lithuania and Ukraine.