WASHINGTON — Counting down to a high-stakes Crimean referendum, President Obama declared Wednesday that the United States would ‘‘completely reject’’ a vote opening the door for the Ukrainian peninsula to join Russia if the election goes ahead on Sunday. Adding pressure on Russia, the Senate advanced a package of potentially tough economic sanctions against Moscow.
Obama made a point of welcoming Ukraine’s new leader to the White House, declaring as they sat side-by-side that he hoped there would be a ‘‘rethinking’’ by President Vladimir Putin of the referendum. Obama derided the vote as a ‘‘slap-dash referendum’’ and warned that if it occurs, the international community ‘‘will be forced to apply a cost to Russia’s violation of international law.’’
Secretary of State John Kerry also was talking tough, telling Congress, ‘‘It can get ugly fast if the wrong choices are made, and it can get ugly in multiple directions.’’ Kerry will meet with Russia’s foreign minister, Sergey Lavrov, on Friday in London in a last-ditch effort to halt the referendum.
Ukraine accused Russia on Wednesday of conducting a large military buildup near the countries’ border that raises the threat of an invasion, but Moscow denied that.
Andriy Parubiy, secretary of Ukraine’s National Security and Defense Council, told reporters in Kiev that Russia has deployed more than 80,000 troops, up to 270 tanks, and 140 combat planes close to the border, creating the ‘‘threat of a full-scale invasion from various directions.’’
Parubiy said Russian troops are based in the immediate vicinity of the Ukrainian border, some as close as a two- or three-hour drive from Kiev.
In Moscow, Deputy Defense Minister Anatoly Antonov denied a military buildup on the nearly 1,250-mile border.
He also said Moscow has accepted a request that Ukraine made Tuesday to conduct a surveillance flight over Russian territory.
Antonov said that while Russia was not obliged to allow such a flight, it decided to issue permission for one so that Ukraine can see for itself that ‘‘Russian armed forces aren’t conducting any military activities near the border of Ukraine that could threaten its security.’’
Russian forces have secured control over Ukraine’s Crimean Peninsula, and Russia’s Parliament has given Putin permission to use the military to protect Russian speakers in Ukraine.
On Wednesday, NATO deployed two surveillance aircraft to monitor Ukraine’s air space and Black Sea ship movements.
Amid the maneuvering, Obama met in the Oval Office with new Prime Minister Arseniy Yatsenyuk, praising him and the Ukrainian people. The meeting was aimed at showcasing the United States’ commitment to Ukraine.
‘‘There’s another path available and we hope President Putin is willing to seize that path,’’ Obama said. ‘‘But if he does not, I’m very confident that the international community will stand firmly behind the Ukrainian government.’’
Yatsenyuk, a 39-year-old pro-Western official who speaks fluent English, defiantly declared that his country ‘‘will never surrender’’ in its fight to protect its territory.
He arrived in Washington seeking financial help to stabilize his fledgling government. The Senate bill that advanced out of committee Wednesday would authorize $1 billion in loan guarantees.
The measure, which next would go to the full Senate, also would allow the Obama administration to impose economic penalties on Russian officials responsible for the intervention in Crimea or culpable of gross corruption.
In the 14-to-3 vote, all committee Democrats supported the measure. Some Republicans expressed concerns about how the United States would pay for the loan guarantees and about provisions to expand the lending authority of the International Monetary Fund.