He was speaking a day after a tense meeting with his Serbian counterpart Aleksandar Vucic in Brussels, where they were hosted by EU foreign policy chief Federica Mogherini.
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A range of sensitive issues remain to be settled between the erstwhile foes, including the question of their common frontier.
This summer, Thaci and Vucic both raised the possibility of redrawing the border, comments that alarmed some observers.
But Thaci, in Paris for WWI commemoration ceremonies this weekend, was clear on one point.
"We will work together to define the borders, just like we did with Macedonia and Montenegro, but there will be no borders based on ethnic lines," he said.
"Kosovo will stay multi-ethnic, Serbia as well, no population displaced. The region will be safer thanks to this agreement."
The countries are seeking an agreement to end a diplomatic deadlock that has lasted for years.
In 2008, a decade after the 1998-1999 war between Serbia's forces and pro-independence ethnic Albanian guerrillas, Kosovo broke away from Serbia.
Serbia -- and its main ally Russia -- refused to recognise Kosovo's independence, although more than 100 countries, including the United States and most EU member states, have done so.
A 'multi-ethnic' army
Despite a tense start to the talks, Thaci remained cautiously optimistic.
"Last evening's meeting was difficult but important for the final phase of the agreement for the normalisation of relations between Kosovo and Serbia," he said.
"I think it is the right momentum and the right leadership to reach an agreement."
Such an agreement would be "about the mutual recognition of Kosovo and Serbia, (a) legally binding agreement, an opportunity for Kosovo to join the UN because Russia will be lifting its veto at the Security council...," said Thaci.
Kosovo's recent decision to create its own army, has provoked anger from its own ethnic Serb minority as well as from Serbia.
NATO, which leads the KFOR military force that ensures Kosovo's security, has also expressed serious reservations.
"I am the president of a sovereign country," Thaci told AFP. "The armed forces of Kosovo will be created. This is a done deal.
"Nobody in Serbia can put a veto on this, whether they like it or not.
"Everything we'll do will be constitutional and legal. This will be a gradual process, coordinated with our partners in NATO and the US," he added.
"It is a new army, peaceful, multi-ethnic, with over 10-percent minority representation."
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