The passage of the U.S. destroyer Truxtun into the Black Sea was seen by official Russian news outlets as a challenge to the Russian fleet and evidence that the U.S. was "ramping up its military presence in the region."

The Russian government-funded RT news network charged that the Truxtun's presence during the Ukraine and Crimea crisis was part of a U.S. buildup in support of Ukraine.

The U.S. Navy has said the Truxtun's movement into the Black Sea was scheduled well before Russia sent troops into Crimea. Navy Cmdr. Andrew Biehn, the Truxtun's captain, the Arleigh Burke-class guided-missile destroyer and the nearly 300 sailors on board would be taking part in joint exercises with the Bulgarian and Romanian navies.

In addition to the Truxtun, the U.S. has sent 12 F-16 fighters and 300 U.S. personnel to Poland this week for a training exercise called in response to the crisis in Ukraine, according to Poland's Defense Ministry.

Last Friday, six U.S. F-15 fighters and a KC-130 tanker arrived in Lithuania to join air police patrols guarding the Baltic states.

Citing previous U.S.-Russian naval faceoffs in the Black Sea, RT reported that the "American battleship is highly unlikely to get anywhere near the Crimea shores, let alone Sevastopol, without a risk of repeating a hasty exit."

That was a reference to the Cold War incident in 1988 in which the cruiser Yorktown and the destroyer Caron were sideswiped by Russian ships in the Black Sea, causing minor damage.

Regional leaders in Russian-speaking Crimea have fast-tracked a referendum on joining with Russia for later this month. The Russian news agency Ria Novosti quoted the speaker of Crimea's Supreme Council, Vladimir Konstantinov, as stating that "the Crimeans will be able to feel as citizens of another country within one month -- within March."

In the run-up to the referendum, the lightly armed Ukrainian troops and naval forces in Crimea have been surrounded and blockaded by troops who have taken off their insignia.

Russian President Vladimir Putin has described the surrounding troops as Crimean "self-defense forces." The U.S. has estimated that at least 20,000 Russian troops are in Crimea.

U.S. leaders have described any attempt to annex Crimea as illegal, but in a Kremlin statement Sunday, Putin said the referendum was "based on international law and aimed at guaranteeing the legitimate interests of the peninsula's population."

In Kiev, acting Ukrainian Defense Minister Ihor Tenyukh issued a list of locations in Crimea where Russian forces were blockading Ukrainian forces.

The list included Ukrainian naval headquarters in Sevastopol; a base in nearby Perevalnoye; a marine battalion in Feodosia on the southern coast; a navy battalion in Kerch on the eastern tip of Crimea; a naval base in Novoozernoye west of Simferopol, the main city and administrative headquarters; and the Belbek military airfield near Sevastopol.

Tenyukh told reporters in Kiev that the Ukrainian ships were also blocked in Sevastopol's outer bay and Lake Donuzlav in the west.

Last Friday, Defense Secretary Chuck Hagel phoned Tenyukh to back "the sovereignty and territorial integrity of Ukraine."

Hagel also "praised the performance and the restraint of the Ukrainian armed forces, who have not allowed the situation to escalate," said Rear Adm. John Kirby, the Pentagon press secretary.

Tenyukh asked Hagel "to consider providing some advice and counsel to his troops with respect to humanitarian assistance and disaster relief efforts," Kirby told the Pentagon press corps on Friday.

In an e-mail statement Sunday, Kirby noted that Hagel and Tenyukh discussed unspecified "technical assistance" beyond humanitarian and disaster relief. Kirby said he didn't want to leave the impression that "there were no other requests, and there have been."

In another show of U.S. support for Ukrainian sovereignty, the White House announced Sunday that President Obama will meet at the White House on Wednesday with acting Ukrainian Prime Minister Arseniy Yatsenyuk.

Obama and Yatsenyuk "will discuss how to find a peaceful resolution to Russia's ongoing military intervention in Crimea that would respect Ukrainian sovereignty and territorial integrity," the White House statement said.

The two "will also discuss support the international community can provide to help Ukraine," the statement said.

The U.S. has already pledged $1 billion in loan guarantees to Ukraine, cut off military-to-military cooperation with Moscow and set up mechanisms for possible economic sanctions and visa restrictions on Russian elites.

-- Richard Sisk can be reached at Richard.Sisk@monster.com.