Top US General Mark Milley spoke by telephone  with his Russian counterpart General Valery Gerasimov, the Pentagon said, amid US warnings that Russia is poised to potentially invade Ukraine.

Milley, the chairman of the Joint Chiefs of Staff, and Gerasimov, chief of the Russian General Staff, “discussed several security-related issues of concern,” said Colonel Dave Butler, the Joint Staff spokesman.

“In accordance with past practice, both have agreed to keep the specific details of their conversation private,” Butler said.

The telephone call is not the first between the two generals but their conversations are rare.

They last spoke on November 23, and discussed Russian troop movements around Ukraine.

The pair met in Finland in September and discussed ways to prevent military incidents between the two countries, according to Moscow.

Butler said Milley also held telephone calls on Friday with counterparts in France, Canada, Germany, Italy, Poland, Romania and Britain.

“The military leaders discussed items of mutual security concern, including ongoing coordination during the adjustment of US force posture in Europe,” he said.

The United States announced Friday it is sending 3,000 more troops to Poland to reassure NATO allies amid heightened fears of a Russian invasion of Ukraine.