German Chancellor Angela Merkel hosts a summit with the leaders of France and Poland Tuesday, less than a month before Berlin takes over the EU presidency amid high hopes that it can resolve power struggles in the bloc.
Tensions between Germany and Poland are threatening to escalate into an EU crisis
The summit in Mettlach, near the French border, will be preceded by a customary meeting between Merkel and French President Jacques Chirac aimed at keeping the traditional dual "motor of Europe" running smoothly.
But the three-way meeting with Polish President Lech Kaczynski needs to soothe tensions between Berlin and Warsaw which has bedeviled Germany's hopes of serving as a bridge between Brussels and the eastern states that joined the EU in 2004.
Kaczynski's conservative government last month strained ties further when it stonewalled the rest of the 25-member bloc's plans to open negotiations with Russia on a new partnership with the EU.
Poland issued the veto in protest at a Russian embargo on Polish meat and plant products, and was called out of line by Merkel's government.
"It (the Warsaw government) is isolating Poland within the European Union," Deputy Foreign Minister Gernot Erler said.
Andreas Maurer from the German Institute for International and Security Affairs (SWP) said the row was giving Merkel an opportunity to show that she can "act as a neutral broker" between Russia and Poland, the biggest of the new, mainly former communist EU members.
But he added that for Berlin, it was "easy to negotiate on behalf of Poland but difficult to negotiate with Poland."
Tensions between Germany and Poland increase
Kaczynski exploited anti-German feelings in Poland
Relations between Berlin and Warsaw have never been warm because of lingering tension over World War II, which Kaczynski exploited to win election, but have worsened since 2003 when Poland backed the US-led invasion of Iraq.
Warsaw is also angry because it will lose transfer fees as a result of a pipeline being built in the Baltic Sea to pump gas directly from Russia to Germany and resents a drive to win recognition for the plight of Germans who were expelled from former German territory, now part of Poland, as the Third Reich collapsed.
Tuesday's summit follows a failed attempt earlier this year to convene the three leaders for the traditional "Weimar Triangle" meeting between their countries, which was first held in 1991.
Kaczynski backed out in July at the height of a row with Berlin over negative coverage in the German press, and has publicly questioned the usefulness of the Weimar meetings.
Franco-German engine running out of steam?
Observer's say the axis is losing its importance
Maurer said the Polish president was not the only skeptic, "The French-German tandem has largely lost its importance, and it is now being called into doubt by the eastern member states."
But he added that Germany will nonetheless face "very high expectations" at the head of the EU.
The bloc in coming months has to cope with the setback in Turkey's membership bid while trying to salvage its bitterly-contested draft constitution.