Gespannen bezoek Merkel aan Polen (en)

German chancellor Angela Merkel is to visit Poland on Friday to emphasize "good relations" between the two countries but rifts over a series of major issues are likely to cast a shadow over the meeting.

The meeting is to cover bilateral relations as well as EU questions.

However, several thorny issues will also be covered by the two sides which have had bumpy relations since the outspoken Kaczynski twins took power.

In the run up to the meeting, the chancellor criticised Poland's decision to have part of the US defence missile shield on its territory saying it should be a NATO decision and not just something decided between Warsaw and Washington.

"We, and I, will say that in Poland we would prefer a solution within NATO and also an open discussion with Russia," she told German public television ZDF.

The issue has become extremely sensitive in Europe. Countries are split on the extent to which NATO should be involved and whether it is worth antagonising Russia, which has been making increasingly strong statements, saying the shield will be used against it. It has also become a major issue for Mrs Merkel's coalition government at home.

The voting question

Meanwhile the other big issue on the agenda is likely to be the EU constitution. Several countries - including France with its uncertain political situation and the UK wanting only a minimalist treaty - will make it hard for Mrs Merkel to get the breakthrough she wants on the EU constitution by the end of her EU presidency.

But Poland is threatening to make it more difficult still by opening the question of who has what power when it comes to law-making in the EU.

"The proposed voting system in the EU constitution mostly hits Poland, according to mathematicians," said prime minister Jaroslaw Kaczynski last week.

The voting system in the constitution - agreed only after major political fisticuffs - takes account of population, meaning Germany has emerged as the country with the greatest voting weight in the legislative council of ministers.

This contrasts starkly with the current voting system under the Nice Treaty whereby Poland - although its population is a lot smaller - has just a little less voting clout than the biggest member states Germany, France and the UK.

If Warsaw goes all the way and opens this issue, it is likely to derail Mrs Merkel's tight schedule for getting a new look EU constitution agreed by the end of this year.

Meanwhile, simmering arguments between the two countries over recent history have cast a constant black cloud over relations - particularly since the Kaczynski's came to power in late 2005.

An exhibition in Berlin on the fate of the millions expelled from their homes in the 20th century, including Germans in the post war period, infuriated Warsaw.

The exhibition is backed by Erika Steinbach, a Christian Democrat politician, and head of the German League of Expellees. Mrs Steinback is also an MP for Mrs Merkel's Christian Democrats.

Although leading CDU members have distanced themselves from remarks she made last week comparing the Polish government to far-right parties in Germany, her comments have added to the tension.