Sigmar Gabriel warned Kosovo it must improve relations with Serbia
Mr Gabriel, who spoke after meeting Kosovan Prime Minister Isa Mustafa, urged the parliament in Pristina to adopt a disputed border deal with Montenegro to unlock a visa liberalisation deal.
He also said he could not give a precise date when Serbia could enter EU, and added that Serbia was a factor of stability in the Western Balkan region.
Mr Gabriel added that Balkan countries must implement reforms and work to overcome age-old divisions if they want to join the EU.
He was due to meet leaders in Serbia and Kosovo this week on his first visit to the region as foreign minister.
Next week, the former economy minister visits Albania.
Mr Gabriel said in a statement: "I will assure my discussion partners: 'The path toward the EU remains open if you choose reforms and progress instead of division and stagnation."
Mr Gabriel said the wounds of the past were still causing tensions
The wounds of the past were still fuelling tensions in the region, he said, noting that there had also been remarkable progress in the Western Balkans in recent years.
We want to support the countries in the region
He added: "We want to support the countries in the region in the development of democracy and the rule of law, and as they move toward stability and prosperity."
His statement came after European Commission President Jean-Claude Juncker warned over instability in the Western Balkans.
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Mr Juncker said to the US Vice President Mike Pence last month: “If we leave them alone – Bosnia-Herzegovina, Republika Srpska, Macedonia, Albania, all those countries — we will have war again.”
Aleksander Vucic is facing protests in Serbia from those who feel his election win was rigged
Many people are resisting the new Serbian President Aleksander Vucic with daily, mass anti-government protests, claiming the election was rigged.
Opposition groups have alleged a crackdown on the media during the campaign and even election day bribes.
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EU commission President Jean-Claude Juncker (R) chats with German EU Commissioner for budget and human resources Guenther Oettinger (L)
Jean-Claude Juncker warned that a war could break out in the Balkans
However, the newly-elected Serbian President is seen by the EU as the nation’s access to the bloc.
The EU is concerned about Russia’s expanding influence in the Balkans, particularly after the Kremlin’s gift of war planes and tanks.