EU foreign-policy chief Federica Mogherini has urged Kosovo's political opposition to ratify a border-demarcation agreement with Montenegro, the last remaining hurdle before it can benefit from visa-free travel to Europe's Schengen zone.
Mogherini on March 4 met with senior officials in Kosovo's capital, Pristina -- the last stop on her tour of the Western Balkans.
She commended Kosovo's leaders for their "constructive stand" in lowering recent tensions with Serbia.
"It's time to vote for the ratification of the agreement. That would release the visa liberalization for the Kosovo people," she said at a news conference with Prime Minister Isa Mustafa.
Mogherini urged opposition political parties to renounce their political interest "and work together for the reconciliatory path to take the country ahead."
The country's opposition has prevented parliament from voting on the border agreement with Montenegro, and another deal with Serbia that gives more powers to ethnic Serbs in Kosovo.
Relations between Kosovo and Serbia have been tense following a series of incidents over the past months.
Mogherini last month summoned Kosovo's and Serbia's presidents and prime ministers twice to Brussels.
Kosovo declared independence from Serbia in 2008, which is recognized by 114 countries but not by Belgrade.
Mogherini's four-day tour of the Western Balkans covered Montenegro, Macedonia, Serbia, Albania, and Kosovo.
She offered reassurance that the European Union's doors remain open for enlargement, although the Western Balkan countries are at different stages of integration into the bloc.
On March 3, Mogherini met with senior Albanian officials and political leaders in Tirana. She reminded them that reforming the justice system and holding free elections were two conditions required for the launching of full EU membership negotiations.
Mogherini's warnings came as hundreds of supporters of Albania's main opposition Democratic Party kept blocking the main thoroughfare in Tirana, saying they don't trust the left-wing government to hold the June 18 parliamentary elections in a fair manner. They want a caretaker cabinet instead.
Albania was granted EU candidate status in 2014.
WATCH: Serbian Nationalists Chant During EU Speech In Parliament
Earlier on March 3 in Belgrade, Mogherini was met with pro-Russian chants and boos in the Serbian parliament as she called for the integration of the Western Balkans into the European Union.
Far-right Serbian legislators, who favor closer ties with Russia over EU integration, banged on benches with their hands and chanted "Serbia, Russia, we don't need the union!" during Mogherini's half-hour speech.
Tensions are on the rise between Serbia and its former foes Bosnia-Herzegovina and EU member Croatia. Serbia has also refused to recognize the Western-backed independence of its former province of Kosovo, a key condition for Belgrade to be accepted into the 28-member EU.
Although Serbia is formally seeking EU membership, deep divisions remain between those seeking pro-Western integration and those wanting a close alliance with traditional Slavic and Orthodox partner Russia.
Several EU leaders have voiced alarm at various issues in the region, with some blaming Russia for attempting to destabilize the region.