The leaders of Germany and Poland have pledged to improve relations between the two countries.
Jaroslaw Kaczynski was greeted in Germany with military honours
In Berlin they discussed two issues souring ties - a gas pipeline that bypasses Poland, and WWII-era claims against the country made by Germans.
Polish PM Jaroslaw Kaczynski reiterated his opposition to the pipeline, but won assurances that Germany would not let Poland be stranded without gas.
He described meeting German Chancellor Angela Merkel as "a good experience".
He said he hoped it would help "build good relations between our countries, between our government and I dare say, maybe also good personal relations".
Supplies from Europe
The two countries have recently had a disagreement over energy security.
The Polish government was incensed when it was not consulted about Germany and Russia's decision to build a gas pipeline under the Baltic Sea, bypassing Poland.
"Poland must not get into a situation in which neighbouring states exert pressure on us with the lever of energy," Mr Kaczynski said.
He reiterated his opposition to the project on Monday, but was placated by Mrs Merkel.
"The idea presented by the chancellor is that in case of a threat [of Russia cutting off gas supplies], Poland will be assured of receiving gas from Western countries," Mr Kaczynski said.
Mrs Merkel insisted that "Poland has a right to access to the European gas market".
Another source of disagreement dates back to World War II.
Warsaw has objected strongly to an exhibition in Berlin that highlights the plight of Germans expelled by Poland after World War II, and to recent reparation claims made by Germans against Poland.
Poland suffered horrifically at the hands of the Nazis and Mr Kaczynski is sensitive to any attempts by Germans to portray themselves as victims, says the BBC's Adam Easton in Warsaw.
Mr Kaczynski wants the two countries to sign an accord ruling out any claims for reparations.
Mrs Merkel said her government did not support such claims, but that an accord "would make things more complicated than they are".
Mrs Merkel has said it is time to bury wartime grievances, and suggested the meeting on Monday was a good start.
"We are both aware of the importance of good relations between Germany and Poland. It is important for both our countries and of great importance for the European Union."