It may not quite have the ring of "Good Morning, Vietnam", but Nick Clegg will introduce himself to the beleaguered populace of Belarus today when he makes a radio broadcast to the people living under Europe's last dictatorship.

The Deputy Prime Minister will take questions from residents in Belarus after speaking to them from Poland via European Radio for Belarus, which is listened to by many of the campaigners battling for new rights under the regime of Alexander Lukashenko. It will be translated into their own language for the radio's website.

Although Mr Clegg is not exactly a household name in the country, EU diplomats believe his act of solidarity will give democracy campaigners a boost. While in Warsaw, he will also meet exiled opposition leaders and dissidents including representatives of the Belarusian Helsinki Committee and the Belarusian Free Theatre.

Mr Clegg will attack the "grave human rights abuses" under Lukashenko's regime. Recalling that he visited Minsk 15 years ago as a European Commission official, he will say that conditions in Belarus are probably worse now than then. But he will detect some signs of hope.

"If we are learning anything from events across the Arab world... it's this: you cannot deny people their rights and freedoms forever. Not in today's world," he will say. "Not when the forces of youth, technology and economic grievance are colliding to drive change across the globe. Pushing the oppressed and forgotten to find their voice. You cannot rig an election, squash dissent, destroy liberty, run an economy into the ground, without, eventually, paying the price."

Mr Clegg will say Lukashenko's support is now at its lowest in years as he finds himself increasingly isolated abroad and facing growing protests at home. He will call on the international community to keep up the pressure, but also tell the regime that dialogue with the EU would still be possible if repression were stopped.

The Deputy Prime Minister is expected to hold informal talks about the eurozone crisis in the margins of the summit with senior EU officials and Angela Merkel, the German Chancellor.

In his speech, Mr Clegg will issue a stark warning that the crisis could lead to the "fragmentation" of the EU, saying this would be a "disaster". He will argue that Britain must not be frozen out if, as expected, euro members adopt greater fiscal integration.

"The problem is if the economic crisis deepens the fault lines between our nations. If it tears us apart," he will say. He will declare that Britain could not accept new rules that would make the eurozone a more important decision-making body over the European Council – the leaders of the 27 EU members including David Cameron.

"It would not be right for the eurozone to take decisions that bind the rest of the EU. Above all, it cannot act against the interests of those who are not members," he will say.