The Kremlin has backtracked after President Vladimir Putin was quoted as saying his military could capture Kyiv in two weeks if he gave the order, while Ukrainian government forces suffered new losses in the fighting against separatists the West says are backed by Russian soldiers.
The Italian newspaper "La Repubblica" reported on September 1 that Putin told outgoing European Commission President Jose Manuel Barroso, "If I want, I can take Kyiv in two weeks."
The newspaper report implied Putin's warning was a response to the possibility the European Union would impose further sanctions on Russia over its role in the Ukraine crisis.
The comment was reportedly relayed by Barroso to leaders at an EU summit on August 30 during which EU leaders decided they should step up sanctions if Moscow does not pull its troops back from Ukraine, where NATO estimated last week that there were more than 1,000 Russian soldiers.
Putin's senior foreign-policy aide, Yury Ushakov, said on September 2 that the remarks were "taken out of context and had a completely different meaning."
He said that "whether the comments were made or not," it was "unworthy of a serious political figure" to reveal details of a private conversation.
Putin's reported remark was the latest in a series of comments that have raised concerns about his intentions toward Ukraine.
Russia annexed the former Soviet republic's Crimea region in March, and the West has rejected its denials that it is supporting pro-Russian rebels who control parts of the eastern regions of Donetsk and Luhansk.
On August 31, Putin called for talks on "statehood" for southeastern Ukraine, though his spokesman said that did not mean Moscow endorsed independence for rebel-held areas.
The pro-Western government in Kyiv says recent gains by separatists, who had appeared to be close to defeat last month, came as a result of Russian military support.
WATCH: Aleksandr Khodakovsky, one of the leaders of the self-proclaimed Donetsk People's Republic, said the Ukrainian military has "no chance" of defeating separatist forces in the country's east. In an interview with RFE/RL correspondent Andrei Babitsky on August 30 in Donetsk, the commander of the separatist Vostok Battalion said former members of the Russian armed forces have been "sharing their expertise" with the rebel forces, but he stopped short of admitting the direct involvement of Russia's regular forces in eastern Ukraine.
Government forces abandoned the international airport outside the city of Luhansk on September 1. A Ukrainian military spokesman on September 2 denied reports the airport in Donetsk had come under separatist control.
Another Ukrainian military spokesman, Andriy Lysenko, said on September 2 that 15 military personnel had been killed and 49 others injured in the previous 24 hours. He did not report losses suffered by the separatists.
UN refugee agency spokesman Vincent Cochetel said on September 2 that the number of people displaced within Ukraine by the conflict has nearly doubled in the past three weeks to at least 260,000.
More than 2,600 people have been killed since the fighting began in April.
The Ukrainian government, NATO, and Western states say Russia has sent troops, artillery, and tanks across the border to reinforce the separatists.
Moscow denies the claim and has accused the Ukrainian government of undermining efforts to reach a negotiated settlement.
Russian Foreign Minister Sergei Lavrov said it was "important" that Ukraine's government and the separatists had discussed ways to resolve the conflict during talks in Belarus on September 1.
But Lavrov on September 2 accused Washington, European countries, and NATO of supporting what he called the "party of war" in Kyiv. He was referring in part to calls by senior Ukrainian officials for the country to abandon its nonaligned status and seek NATO membership.
NATO, at a summit this week, is expected to agree on plans to boost its military presence in Central and Eastern Europe amid heightened concerns in member states near Russia's borders about Moscow's possible intentions.
A senior Russian official said NATO's plans were "evidence of the desire of U.S. and NATO leaders to continue their policy of aggravating tensions with Russia."
Mikhail Popov, the deputy head of Russia's National Security Council, said deteriorating relations with the United States and NATO will be reflected when Russia's 2010 defense doctrine is adjusted later this year.
NATO says the planned rotation of troops and equipment will not breach an agreement struck with Russia in 1997, limiting its presence in Eastern Europe.
U.S. President Barack Obama is expected to arrive in Baltic NATO-member Estonia on September 2 before heading to Britain for the alliance's summit.
Ahead of the visit, Estonian President Toomas Hendrik Ilves said his country wants NATO to set up permanent bases on its territory to protect it against potential threats from Russia. Any such move would anger Moscow.
Russia's annexation of Crimea and the conflict in eastern Ukraine have driven relations between Moscow and the West to post-Cold War lows and prompted exchanges of punitive sanctions.
As part of a new sanctions package that is under consideration, the European Union is reportedly considering adding Defense Minister Sergei Shoigu to a list of Russians barred from entering the EU.
Reuters news agency reported that the proposal was floated by the European Commission during a meeting of EU ambassadors on September 2.
The commission is also proposing widening bans to prohibit all state-owned Russian firms from borrowing or raising capital in Europe and to bar the export of goods that can have both military and civilian uses to all potential Russian importers, not just those in the defense sector.
EU governments are to make a decision on the final shape of the new sanctions by September 5.
With reporting by Reuters, AFP, and Interfax