German Foreign Minister Frank-Walter Steinmeier called on both Russia and Ukraine to better control their common border ahead of a meeting with his Russian counterpart Sergei Lavrov.
"[It is about ensuring] there is common border management in some form," said Steinmeier shortly before the meeting, which will also include Poland's foreign minister.
Steinmeier added that the situation in eastern Ukraine must be stabilized and that it was important to ensure a substantial exchange develops between Russian President Vladimir Putin and Ukraine's new president, Petro Poroshenko.
The two met briefly in France last week at a World War II anniversary event.
On Monday, Ukraine said it had reached a "mutual understanding" with Moscow on parts of a plan proposed by Poroshenko for ending violence in the east of the country.
The Polish Foreign Minister Radoslaw Sikorski emphasized his worries about the situation in eastern Ukraine.
"We will explain to our Russian colleague the concern that we feel in the European Union at the destabilization of eastern Ukraine," said Sikorski before the talks.
Scores of people have been killed since April in eastern Ukraine, including separatists and government forces. But fighting has ebbed in the past few days despite renewed shelling of rebels in the city of Slovyansk.