A senior U.S. official on Saturday met with top Kosovo leaders in an attempt to persuade Pristina to revoke or suspend a tariff on Serb goods so that dialogue with Serbia can resume.

Under Secretary of State for Political Affairs David Hale is the latest U.S. envoy to take part in shuttle diplomacy between Pristina and Belgrade. He met with Kosovo's president, speaker and prime minister. A day earlier, he was in Belgrade.

Kosovo Prime Minister Ramush Haradinaj has resisted U.S. calls to suspend the tariff, saying it will only be lifted when Belgrade recognizes Kosovo's sovereignty and stops preventing it from joining international organizations.

Serbia says it will not take part in the European Union-facilitated discussions until the 100-percent tax is lifted.

Since 2011 the two former war foes have been in a EU-facilitated dialogue, aiming at resolving the long-standing Balkan dispute. Brussels has told both countries they must normalize their ties before they can hope to join the bloc.

Earlier this week Kosovo's Parliament adopted a negotiating platform for the talks that involves mutual recognition and keeping the current borders intact.

Belgrade responded that this was a rigid platform that dashes all hopes for a compromise solution.

Kosovo President Hashim Thaci said Saturday Belgrade should not condition the dialogue, which should be ``comprehensive and transparent.''

Thaci said the leaders told Hale that ``the status quo and the situation of a frozen conflict are inadmissible.''

Serbia doesn't accept Kosovo's 2008 declaration of independence.