Serbian Prime Minister Ivica Dacic announced that the "integrated border management" agreement, which was finalized in meetings last week between himself, Kosovo Prime Minister Hashim Thaci and EU High Representative for Foreign Affairs Catherine Ashton, was put into force without incident.
The agreement was reached last year under the former Belgrade government headed by the now-opposition Democratic Party and were continued with ambivalence by Dacic's more nationalistic Socialist-led government, which took power in July.
It is seen as a crucial step in stabilizing the border with its former province, which asserted its independence in 2008 but isn't recognized by Serbia.
Its provisions call for the EU civilian mission EULEX to oversee the transition of control over the border jointly to both sides with the aim of ending a power vacuum that has resulted in rampant smuggling and other illegal activities along the frontier.
The agreement's implementation has also been a key demand of the European Union for a setting a date to begin Serbia's accession process, now expected for June.
Dacic said his meeting with Thaci and acceptance of the border deal shows Serbia remains serious about finding a lasting solution with Kosovo.
"Throughout the agreement on integrated management of administrative crossings, the Serbian government has confirmed its credibility, and that it is aware of the responsibilities and commitments of the previous government," Dacic said.
The new border regime was instituted at the Jarinje and Merdare crossings, with two more gates to be included beginning Dec. 31. It gives ethnic Serbs living in northern Kosovo assurances they won't be charged customs duties on goods transported into the territory, the Voice of Serbia reported.
It also provides they will be able to use personal documents and vehicle registration plates issued by the Serbian Interior Ministry to cross the border.
EULEX spokeswoman Irina Gudeljevic said the implementation of the border management deal is good news for the troubled region.
"We are extremely satisfied with the implementation of the existing agreement between Belgrade and Pristina," she told the Serbian news agency Tanjug. "As always, EULEX supports all the agreements Belgrade and Pristina are ready to implement and we will continue to do so in the future.
"The important thing is that we work as a team here," she said.
Fisnik Rexhepi, the head of Kosovo's working group on the border agreement, told the Balkan Investigative Reporting Network the new border regime would continue as long as both sides respect its provisions.
"The agreement will be implemented based on the show of good will by both parties," he said. "If there is no such good will on Serbia's side, there is no reason for us to continue the implementation of the agreement."
Kosovo Deputy Prime Minister Edita Tahiri told the Turkish newspaper Today's Zaman the agreement represents a recognition of Kosovo's territorial integrity by the Serbs.
"Most of the Serbs living in Kosovo have accepted the fact that Kosovo is an independent state," Tahiri said. "They have become part of the state, the government and Parliament.
"However, the Serbian population in the north have held illusions about this fact. They are confused whether they are part of Serbia or Kosovo. This agreement will put an end to the illusion. Citizens want normalization."