The Western-backed regime in Ukraine announced Thursday that it was placing its military forces on the highest state of combat alert amid the ratcheting up of tensions with Russia in the wake of a reported terrorist provocation in Russian-ruled Crimea.

For its part, Moscow announced the staging of maneuvers in the Black Sea, with the Russian navy rehearsing tactics for the repulsion of a attack on Crimea.

The Ukrainian government, which on Thursday sent its ambassador to the United Nations to speak before the Security Council on the matter, charged that Russia has massed more than 40,000 troops in Crimea and on the Ukrainian border. As Crimea is the historic base of Russia’s Black Sea fleet, it has always had a large deployment of the country’s military.

Russia’s ambassador to the UN, Vitaly Churkin, dismissed the charge, declaring, “Instead of counting our military, they should be bringing an end to the conflict” in eastern Ukraine, where the Kiev government’s forces have continued to attack a separatist Russian-speaking minority, claiming some 10,000 lives since April 2014.

Moscow has charged the Ukrainian government with organizing a terrorist attack aimed at striking vital infrastructure inside Crimea, a territory that Russia annexed following a plebiscite in which the peninsula’s population voted for unification with Russia. The move followed the February 2014 coup, orchestrated by Washington and Germany and spearheaded by ultra-nationalist and fascist forces, which overthrew the elected, pro-Russian government of Viktor Yanukovych and installed a rabidly anti-Russian regime. The United States backed the putsch in a bid to escalate the US-led drive to encircle and militarily subjugate Russia.

A NATO official told the AFP news agency that the US-led military alliance was carefully following the rising tensions between Russia and Ukraine, declaring that “Russia’s recent military activity in Crimea is not helpful for easing tensions.”

State Department spokesperson Elizabeth Trudeau called the situation “very dangerous” and reiterated Washington’s position that “Crimea is part of Ukraine.”

Both dismissed Russia’s account of terrorist actions against Crimean territory by a Ukrainian-organized special operations squad.

Russia’s state security agency, the FSB, issued a detailed statement Wednesday, saying that the attacks were carried out on the night of August 6-7 under the direction of the Main Intelligence Directorate of the Ministry of Defense of Ukraine. Further attempts at infiltration were repeated on August 8.

The statement said that one FSB agent was killed in the attempt to detain the Ukrainian operatives, whose object was described as the targeting of “critical infrastructure and life support facilities” in Crimea. A Russian soldier also was reportedly killed by fire from Ukrainian military units, including armored vehicles, in support of the operation.

The FSB claimed to have recovered “20 improvised explosive devices with a total explosive power of 40 kg [of] TNT,” along with land mines, grenades and special assault weapons.

The agency also presented evidence it said was given by a Ukrainian described as an operative of Ukrainian military intelligence and a leader of the special operations units, identified as Yevgeniy Aleksandrovich Panov.

Sergei Aksyonov, Crimea’s prime minister, charged that the real source of the terrorist operations was Washington. “Ukrainian officials wouldn't have had the courage for such actions ... These are not their own actions and messages,” he said, adding, “the US State Department is looming behind them.”

There is every reason to suspect that this is the case. The provocation in Crimea comes in the midst of a drumbeat of escalating US rhetoric and actions taken against Russia. The US has stepped up its arming and funding of Al Qaeda-linked militias in Syria in an attempt to reverse the victories of Syrian government forces, which have been closely supported by Russian air power. On August 1, the US-backed jihadists shot down a Russian helicopter on a relief mission, killing all five aboard. In the media, former top officials and columnists with close government connections have called for US air strikes against the Russian-backed forces and the imposition of a “no-fly zone” that would inevitably spell a confrontation with Russia’s air force.

In Ukraine itself, Washington has worked to build up the military of the crisis-ridden, right-wing regime in Kiev headed by the oligarch Petro Poroshenko. A 500-strong US unit is presently on the ground in western Ukraine training Ukrainian forces, including members of fascist-led militias, while hundreds, if not thousands, of other US military personnel and contractors are regularly rotating in and out of the country. Last month, the US Navy joined with Ukrainian warships in the “Sea Breeze” exercises aimed at challenging Russia in the Black Sea. In July, US Secretary of State John Kerry visited Ukraine for talks with Poroshenko, where he reiterated Washington’s support for the Kiev regime’s claims on Crimea.

The dangerous war tensions between Ukraine and Russia have been unleashed in the midst of an election campaign that has seen the presidential front-runner, Democratic candidate and ex-Secretary of State Hillary Clinton, attack the fascistic Republican candidate Donald Trump from the right, particularly over the question of Russia.

The Democrats have staged a neo-McCarthyite campaign against Trump, accusing him of being a puppet of Vladimir Putin, while also charging—with no evidence—that the Russian president was behind the WikiLeaks release of Democratic National Committee emails exposing attempts to rig the primaries against Clinton’s challenger, Senator Bernie Sanders.

Among the charges leveled against Trump—again without substance—is the assertion that his campaign “watered down” the Republican platform’s language on Ukraine. The language, in fact, denounces the Obama administration for abetting a “resurgent Russia,” backs sanctions against Moscow, and calls for “appropriate assistance to the armed forces of the Ukraine.” The complaint was that it left out a reference to supplying them with “lethal weapons,” something the Obama administration itself claims it is not doing.

That Clinton attacks such policies from the right, with growing support from key figures in the US military and intelligence apparatus along with growing numbers of Republican policy makers, constitutes a clear warning. Preparations are being made for a direct military confrontation with Russia in eastern Europe, with provocations like those staged in Crimea serving as the likely trigger. Whether such a dangerous escalation of conflict, involving the world’s two major nuclear powers, will be postponed until after November is itself an open question.