MOSCOW — Russia is gathering thousands of troops, artillery and other equipment at its border with Ukraine as part of military training exercises that also serve as a blunt reminder of Russia’s ability to easily move deeper into the neighboring country.
The exercises are scheduled to take place over the next two weeks amid a standoff with the United States and Europe over the fate of Ukraine’s Crimea region — currently occupied by Russian troops.
A referendum is set in Crimea for Sunday over whether the autonomous region should secede from Ukraine and join the Russian Federation. US President Barack Obama and European leaders have promised economic and diplomatic retaliation if that happens.
As negotiations continued, the Russian Defense Ministry reported on its website that 1,500 paratroopers would be dropped along with their equipment into the Rostov region near the border with Ukraine to conduct exercises over the next two weeks.
Over the last few days, Russian armored vehicles have been spotted in Belgorod, farther to the north. The Defense Ministry said the exercises included 8,500 artillery troops, along with an assortment of rocket launchers, howitzers, antitank guns and other weapons.
‘‘The main goal of the ongoing events is to comprehensively assess the units’ teamwork and subsequently tackle combat training tasks on an unfamiliar terrain and untested training ranges,’’ the ministry said in a statement.
Russia offered the description of its military movements a day after Ukrainian officials complained of a military buildup on its borders. Andriy Parubiy, secretary of Ukraine’s National Security and Defense Council, said Wednesday in Kiev that Moscow had amassed perhaps 80,000 troops, along with tanks and combat aircraft, on the border with eastern Ukraine, which he said was tantamount to an invasion threat.
Though the exercises are not confined to the Ukraine border region — they will also be conducted in central Russia — the signal is a strong one.
‘‘In general terms, this is what a military does if it wants to keep at readiness,’’ said Mark Galeotti, a New York University professor who studies Russian security. ‘‘But in circumstances like this, they’re very aware of the political implications of any movements.’’
Galeotti, who is in Moscow, said paratroopers are mobile and good at sealing off an area, but they would need regular troops to back them up quickly in case of serious conflict. ‘‘What they are not good at is relatively hard-core military combat,’’ he said.
The crisis over Crimea, a region with strong ties to Russia, has developed into perhaps the worst standoff between Russia and the West since the end of the Cold War. It began last month when the pro-Russian Ukrainian government of President Viktor Yanukovych was toppled after mass protests, and a new leadership took power with the blessing of European nations and the United States.
Russia promptly moved troops into Crimea and is hosting the deposed president, who has vowed to reclaim power.
U.S. Secretary of State John Kerry is scheduled to meet Russian Foreign Minister Sergei Lavrov in London on Friday to seek a diplomatic resolution.
Kerry appealed to Congress on Thursday to back International Monetary Fund reforms that are required for delivery of some of the proposed financial aid to Ukraine.
Kerry told the Senate Appropriations subcommittee on foreign operations that he does not know whether Russian annexation is a foregone conclusion, but he acknowledged ‘‘strong indications’’ that former defense secretary Robert Gates is right in saying that Crimea is now lost to Ukraine.
‘‘There are other . . . thoughts out there that suggest that something short of a full annexation might also be achievable,’’ Kerry told the panel.
Obama met with Ukraine’s interim prime minister, Arseniy Yatsenyuk, at the White House on Wednesday and said the United States and its allies would ‘‘apply a cost’’ to Russia if it tries to divide the Crimean region from the rest of Ukraine.
German Chancellor Angela Merkel emphasized the point in a speech Thursday to the German parliament that recalled Europe’s centuries of strife over ‘‘spheres of influence and territorial claims,’’ news services reported from Berlin.
‘‘I’m afraid we have to dig in for the long haul to solve this conflict,’’ she said, with sanctions against Russia expected early next week if the Sunday secession vote proceeds.
‘‘If Russia continues on the course of the last weeks, it won’t just be a catastrophe for Ukraine,’’ Merkel said. ‘‘It would also cause massive economic and political harm to Russia.’’
Pro-Russia forces continued to expand onto Ukrainian military facilities in Crimea on Thursday. About 100 armed militiamen from self-defense units came by bus to an oil warehouse on a base near the train station in the Crimean regional capital, Simferopol, said Vladislav Seleznyov, a spokesman for the Ukrainian military. He said the Ukrainian troops on the base are unarmed, and as of midday Thursday the base commander was still negotiating with the militia.
In a separate incident, he said a Russian navy ship was scuttled at the entrance to the bay at Donuzlav in northern Crimea, blocking Ukrainian navy ships from leaving. It is the third ship deliberately sunk to impede naval traffic, he said.
As Russia’s grip in Crimea tightened, European nations and the United States have been discussing a variety of responses, including visa restrictions and economic sanctions.
The largely European Organization for Economic Cooperation and Development (OECD) said Thursday it is giving Russia the cold shoulder for the moment, postponing consideration of Russia’s membership at the request of its 34 member nations.
In a written statement, the OECD also said it would work to help out the ‘‘public policy challenges’’ faced by Ukraine, which is not a member.
Russian Deputy Prime Minister Dmitry Rogozin said Thursday on Twitter that he plans to meet with leaders of major companies to discuss what measures to take if the West imposes sanctions on Russia because of its intervention in Ukraine.
Morello reported from Sevastopol. Washington Post staff writer Anne Gearan in Washington contributed to this report.