The United States has accused Russia of fabricating an attack by Ukrainian forces as a pretext to invade.
Pentagon spokesman John Kirby said Washington has credible intelligence about an elaborate Russian plot, amid heightened tensions.
Moscow has been accused by the US of producing a graphic propaganda video of staged explosions and corpses, as well as actors depicting grieving mourners.
The alleged plans for a fake attack on Russian territory or Russian citizens have been shared with Ukrainian officials and European allies in recent days.
It is the latest allegation by the US and the United Kingdom that Russia is plotting to use a false pretext to go to war against Ukraine.
“We’ve seen these kinds of activity by the Russians in the past, and we believe it’s important when we see it like this, and when we can, to call it out,” Kirby told reporters at the Pentagon.
Kirby stated that Moscow would also stage military equipment used by Ukraine and the West to support the alleged scheme.
UK Foreign Secretary Liz Truss said the US intelligence "is clear and shocking evidence of Russia's unprovoked aggression and underhand activity to destabilise Ukraine".
The Kremlin has rejected the accusation it is about to invade Ukraine. It has issued a list of demands, including a guarantee that Ukraine will never join NATO.
It has also accused the US of stoking "hysteria" over Ukraine and aggravating the situation by sending more troops to eastern Europe.
Responding to Kirby's allegations, Vladimir Putin's spokesman, Dmitry Peskov, said "not to take their [the US'] word for it".
The US intelligence claims come as Turkish President Recep Tayyip Erdogan offered to mediate talks between Russia and Ukraine.
Erdogan said on Thursday that Ankara was “prepared to undertake its part in order to end the crisis between two friendly nations that are its neighbours in the Black Sea.”
“I have stressed that we would be happy to host a summit meeting at a leadership level or technical level talks,” Erdogan said after talks with Zelenskyy.
“Instead of fueling the fire, we act with the logical aim of reducing the tensions," he added.
The Ukrainian President welcomed Erdogan’s offer and thanked him for his “firm and consistent” support.
Russia has amassed more than 100,000 troops near Ukraine’s northern and eastern borders, raising NATO concerns of an invasion -- something Moscow has denied.
NATO has warned that Moscow’s military buildup continues, with more troops and military equipment deployed to neighbouring Belarus than at any time in the last 30 years.
“Over the last days, we have seen a significant movement of Russian military forces into Belarus. This is the biggest Russian deployment there since the Cold War,” NATO Secretary-General Jens Stoltenberg told reporters.
Stoltenberg renewed his call for Russia to “de-escalate,” and repeated warnings from the West that “any further Russian aggression would have severe consequences and carry a heavy price.”
NATO has no intention of deploying troops to Ukraine should Russia invade, but it has begun to reinforce the defenses of nearby member countries.
Washington announced on Wednesday that it would deploy an additional 3,000 troops mostly in Poland and Romania on a temporary basis due to the ongoing situation with a further 8,5000 forces in the US put on a "heightened" state of readiness.
Russian President Vladimir Putin discussed the ongoing situation with his French counterpart Emmanuel Macron in their third telephone conversation of the week.
Moscow has demanded "security guarantees," the Kremlin said in a statement, referring again to "provocations" by Ukraine.
"A constructive dialogue continued on the issues of Ukraine and the Russian initiative to establish long-term legal guarantees for the security of the Russian Federation."
Zelenskyy, who also discussed the situation with Macron on Thursday evening, said the two leaders discussed "countering security challenges and stepping up the peace process within the Normandy Format" which also includes Germany and Russia.
He added that they "agreed on further joint steps to maintain Ukraine's stability and enhance financial-economic cooperation."