WASHINGTON

The Pentagon said Thursday it is closely monitoring the "fluid" situation regarding clashes between Azerbaijan and Armenia.

"We have carefully structured all of our assistance to both Azerbaijan and Armenia to ensure that it is not in any way associated with the conflict between the two nations," Pentagon spokesman Col. Thomas Campbell told Anadolu Agency.

“The current situation is fluid,” he said.

Pentagon condemns the violence and offered condolences to the families of those killed and injured.

"The United States urges the sides to cease hostilities immediately and work with the Minsk Group co-chairs to return to substantive negotiations as soon as possible," Campbell added.

Relations between the two former Soviet republics have been volatile since 1991 when the Armenian military occupied Upper Karabakh, an internationally recognized territory of Azerbaijan.

New border attacks Sunday by Armenia escalated longstanding tensions.

World powers, including the US, Russia, France and Germany, have urged an immediate halt to clashes along the frontier.

Turkey, meanwhile, has voiced support for Azerbaijan, and its right to self-defense.

Four UN Security Council and two UN General Assembly resolutions, as well as many international organizations, demand the withdrawal of occupying forces.

The OSCE Minsk Group -- co-chaired by France, Russia, and the US -- was formed in 1992 to find a peaceful solution to the conflict, but to no avail. A cease-fire, however, was agreed to in 1994.

*Kasim Ileri contributed to the story