With tens of thousands of Russian troops massing on Ukraine's borders, efforts have intensified to prevent a conflict and US Secretary of State Antony Blinken was preparing to fly to Kyiv for talks on Wednesday.
Blinken's trip, which will also take him to Berlin for meetings Thursday with European allies, is the latest in a flurry of diplomacy to prevent the tensions over Ukraine from escalating into a new war in Europe.
Talks in Geneva, Brussels and Vienna last week failed to ease fears, with Russia insisting its demands for sweeping security guarantees -- including a permanent ban on Ukraine joining NATO -- be taken seriously.
Russian Foreign Minister Sergei Lavrov said Tuesday that there would be no further negotiations until the West gives it proper answers.
"We are now awaiting responses to these proposals -- as we were promised -- in order to continue negotiations," he said at a joint press conference with visiting German Foreign Minister Annalena Baerbock.
"Let's hope these talks will continue," Lavrov said.
Washington has outright rejected the demands, which also include limits on allied deployments in former Warsaw Pact allies like Poland and the ex-Soviet Baltic states that joined NATO after the Cold War.
In a call with Lavrov ahead of his trip, Blinken "stressed the importance of continuing a diplomatic path to de-escalate tensions," State Department spokesman Ned Price said.
NATO chief Jens Stoltenberg also left the door open to more talks, saying he had invited Russia and NATO allies to a series of discussions in the NATO-Russia Council "in the near future".
The aim is to "address our concerns but also listen to Russia's concerns, and to try to find a way forward to prevent any military attack against Ukraine," Stoltenberg told a news conference in Berlin.
The State Department said Blinken would fly to Ukraine and meet with President Volodymyr Zelensky on Wednesday, to "reinforce the United States' commitment to Ukraine's sovereignty and territorial integrity".
Belarus military drills
Blinken will head to Berlin on Thursday for four-way talks with Britain, France and Germany on the Ukraine crisis.
The four countries will discuss "joint efforts to deter further Russian aggression against Ukraine, including allies' and partners' readiness to impose massive consequences and severe economic costs on Russia," Price said in a statement.
According to respected Russian newspaper Kommersant, Blinken and Lavrov have also agreed to hold talks in Geneva on Friday.
Ukraine, the United States and European countries have all raised deep concerns over the Russian troop build-up, despite repeated denials from Moscow that an invasion is planned.
Kyiv has been at war with pro-Moscow separatists in the east of the country since 2014, when Russia annexed the Crimean peninsula from Ukraine after demonstrations ousted a Kremlin-aligned leader.
Adding to the tensions, Russia and Ukraine's neighbour Belarus on Tuesday launched snap military exercises.
The Belarusian defence ministry said it was hosting the combat readiness drills because of the continuing "aggravation" of military tensions "including at the western and southern borders of the Republic of Belarus."
Ukraine borders Belarus to the south and NATO member Poland to the west.
Neither Moscow nor Minsk has disclosed the number of troops involved, but a video published by the Belarusian defence ministry showed columns of military vehicles including tanks being unloaded from trains blanketed in snow.
Warning from Turkey
NATO member Turkey also warned Moscow against invading Ukraine, with President Recep Tayyip Erdogan saying on Tuesday that he intends to discuss rising tensions with Russian President Vladimir Putin.
"I don't see Russia's invasion of Ukraine as a realistic option because it is not an ordinary country. Ukraine is a powerful country," Erdogan told reporters in Albania.
Turkey has supplied combat drones to Ukrainian forces, drawing fierce criticism from Moscow.
Russian negotiators met separately this month with delegations from the United States, NATO and the Organization for Security and Co-operation in Europe (OSCE), in meetings that failed to produce any concrete results.
British Defence Secretary Ben Wallace announced in parliament on Monday that Britain is sending weapons to Ukraine as part of a package that would help Kyiv secure its borders.
The types of equipment being sent "are not strategic weapons and pose no threat to Russia," he said, describing them as "light, anti-armour, defensive weapon systems".
Kremlin spokesman Dmitry Peskov on Tuesday described the announcement of the shipments as "extremely dangerous" and "not conducive to reducing tensions".