Krynica (Poland) (AFP) - European military assistance to Ukraine could lead to a nuclear conflict between Russia and NATO, according to Poland's iconic cold warrior and Nobel Peace Prize laureate Lech Walesa.

"It could lead to a nuclear war," the anti-Communist legend told reporters when asked whether the EU should send weapons to Ukraine to help it fights off separatist rebels and Russian aggression.

"The EU is well aware that Russia has nuclear weapons. NATO has them too. Must we then destroy each other?" said the former Solidarity trade union leader famous for negotiating a bloodless end to communism in Poland in 1989.

"This is why the EU keeps on repeating: stop being silly (...) This is why it isn't getting involved too much!" he added, at an annual regional economic in Krynica, southern Poland.

The EU on Saturday agreed to impose fresh sanctions on Russia should Moscow failed to change its behaviour in Ukraine, after Kiev said Russian soldiers were fighting along side pro-Moscow rebels.