Poland's President Andrzej Duda held a phone conversation with his German counterpart Frank-Walter Steinmeier, shortly before the latter's visit to Moscow, President's top aide Krzysztof Szczerski said on Wednesday.

Their conversation focused on Ukraine and Russia's recent proposal (to deploy UN peace-keeping forces in eastern Ukraine - PAP), Krzysztof Szczerski went on to say.

President Steinmeier declared that he would try to speak with Russian President Vladimir Putin about "indeed a real problem for Poland, namely, the keeping by Russia of the Smolensk disaster evidence".

"President Steinmeier goes to Moscow for the ceremony but he will also have political talks with President Putin. And he found it appropriate to make a phone call to the Polish head of state to hold consultations before his visit", minister Szczerski said.

According to Szczerski, Ukraine was the most important topic since it is "a case of common concern for Poland and Germany". "The presidents spoke about Russia's recent proposal to deploy UN peace-keeping forces in eastern Ukraine", the presidential minister added.

President Duda also underlined that the Smolensk air crash, especially Russia's continuous detainment of the main evidence in the case, was indeed a problem in Polish-Russian relations, Szczerski told PAP.

Minister Szczerski emphasised that President Steinmeier promised he would try to speak about this issue with his Russian counterpart. (PAP)