Success of dialogue between Serbian and Kosovan leaders can only be measured by finding a "sustainable solution" for all, the EU's foreign policy chief said on Thursday.
Kosovo -- a former Serbian province -- declared independence in 2008 and is recognized by over 100 countries, including the U.S, the U.K, France, Germany and Turkey.
Belgrade insists the territory is still part of Serbia.
In 2011 a Serbia-Kosovo dialogue was initiated by the EU, as it believes Serbian recognition of Kosovo should be the ultimate goal of negotiations.
Since then, negotiation teams from both states have been holding talks in Brussels.
Mogherini's remarks came at a joint news conference with Serbian Prime Minister Ana Brnabic.
Brnabic and Mogherini were in Brussels at a fourth meeting of the Stabilization and Association Council between Serbia and the EU.
Mogherini praised a new phase of dialogue between Belgrade and Pristina, the direct participation of the two presidents, with a change in the format, agenda and speed of the meetings.
"The dialogue is about normalizing the relations between Belgrade and Pristina, and its success is not measured by speed, but by the progress in normalizing the relations of the two sides, which is measured by finding a sustainable solution for all," said Mogherini.
Serbia's government has set EU integration as a main goal while holding its natural position as a traditional ally of Russia, meaning Belgrade needs to build relationships with its neighbors.
Brnabic said Belgrade was fully committed to the Kosovo process and praised the "courageous decision" of Serbian President Aleksandar Vucic to launch an internal dialogue.
Vucic has called on Serbian citizens to hold an "internal dialogue" on Kosovo.
In late October, Serbia announced the formation of a "working group" for the second phase of this dialogue.
