NATO is relocating staff from Ukraine's capital Kiev to Lviv, in the west of the country. The alliance is also repatriating some staff, transporting them to Brussels for their "safety", an official announced Saturday.

"The safety of our personnel is paramount, so staff have been relocated to Lviv and Brussels. The NATO offices in Ukraine remain operational," the official told AFP, not giving the agency any figures on how many representatives the alliance was relocating to either destination.

Several Western countries have already relocated their diplomats from Kiev to the Western part of Ukraine, near the Polish border, citing "Russian military action."

The NATO official also said, "NATO and allied countries are monitoring and assessing the situation very closely, and [they] continue to take all the necessary measures."

The United States dominates the alliance, and its president, Joe Biden, said Friday he was convinced Moscow would invade Ukraine within the week, in the latest US prediction of when Russia would "invade".

Washington has several times changed the timeframe of when the alleged Russian invasion would take place, though the US has stressed that it was "confident" with its intelligence on the matter.

US Secretary of State Antony Blinken said Saturday Washington was confident in its intelligence about the current situation around Russia and Ukraine that the United States was receiving and making public.