"The competent defense and security organs of Serbia consider the KSF a direct threat to our national security, and to peace and stability as a whole in the western European region," B92 radio quoted Jeremic as saying.
On Tuesday, the Kosovo Protection Corps was dissolved and replaced by the Kosovo Security Forces, Serbian news web site B92 reported earlier.
According to the Serbian diplomat, the creation of the "illegal formations" of the KFS is a "gross breach of UN Security Council Resolution 1244" and Belgrade's representatives in the United Nations and NATO plan to voice their resolute protest.
"Serbia will use all of its diplomatic efforts to reverse this decision," the minister was quoted as saying.
On Wednesday in Kosovo's capital, Pristina, a ceremony was held to mark the official start of the new force's activities.
"We are entering a new phase, the forces have become a reality," the KSF chief, General Sylejman Selimi, said during the ceremony.
The Kosovo Security Forces will have 2,500 active members and 800 reserve members. The new force will receive training from the British Army and supplies from the United States and Germany.
Serbia does not recognize Kosovo's independence, which was unilaterally claimed in February last year and has been affirmed by more than 50 countries, including the United States and most European Union member-states. Russia and Serbia consider Kosovo a Serbian province.
