Moscow has stationed thousands of troops on Ukraine's border and in annexed Crimea, EU says, with its top diplomat Josep Borrell warning "the risk of further escalation is evident."
Russia has stationed "more than 100,000" troops on Ukraine's border and in annexed Crimea, according to the European Union statement, while the Pentagon said that Moscow's military buildup is larger than that in 2014.
The European Union on Monday slashed its estimate of the numbers of Russia troops along the Ukraine border from 150,000 to more than 100,000, correcting a statement earlier in the day.
But in the revised statement online, EU foreign policy chief Josep Borrell still warned that the Russian troop build-up was "very concerning", adding: "The risk of further escalation is evident."
Earlier, Borrell had said Russia had massed over 150,000 troops along the Ukrainian border and in the annexed Crimea peninsula, in comments to journalists following talks involving Ukraine's foreign minister.
But he refused to disclose the source of the figure.
In a statement put online on Monday evening, the figure quoted by Borrell had been revised down to "more than 100,000". A footnote explained that the figure had been corrected, but with no further explanation.
Largest-ever military buildup
Later on Monday, Pentagon said, "It is certainly bigger than the one in 2014."
Pentagon spokesman John Kirby declined to provide a specific number.
It was not clear if the movement of troops was for training purposes.
He said no new economic sanctions or expulsions of Russian diplomats were planned for the time being, despite saying that the military buildup on Ukraine's borders was the largest ever.
Ukraine wants sanctions on Russia
A US official, speaking on the condition of anonymity, said the Russian build-up numbered in the tens of thousands but was not aware of intelligence that pointed to more than 150,000 Russian troops.
Ukrainian Foreign Minister Dmytro Kuleba, after addressing EU foreign ministers, called on the EU to impose new sanctions on Russia.
Tensions between Moscow and Kiev have been rising amid the military build-up and clashes in eastern Ukraine between the army and pro-Russian separatists.