Britain, Poland and Ukraine are working to strengthen their trilateral cooperation in the face of the threat of a new Russian military intervention, leaders of the two Eastern European countries said in Kyiv, Reuters reported.

British Prime Minister Boris Johnson is scheduled to arrive in Kyiv later on Tuesday.

"I hope that in the near future we will be able to officially launch a new regional format of cooperation Ukraine-Poland-UK, in the context of ongoing Russian aggression, we should sign a trilateral document on cooperation to strengthen regional security," said Ukraine's Prime Minister Denys Shmygal.

Speaking at a joint news conference with Shmygal, his Polish counterpart Mateusz Morawiecki said Warsaw would help Ukraine with gas and arms supplies, as well as humanitarian and economic aid.

"Living close to a neighbour like Russia we have the feeling of living at the foot of a volcano," said Morawiecki, adding Warsaw would provide Ukraine with artillery ammunition, mortars, portable air-defence systems and surveillance drones.

Morawiecki urged Germany not to launch the Nord Stream 2 pipeline, saying it poses serious security risks. 

"Through launching this pipeline, Berlin is loading Putin's pistol, which he can then use to blackmail the whole of Europe," he said.

Morawiecki said foreign ministers were "working on a potential format that could tighten cooperation on various fields between Poland, Ukraine and Britain."