A Russian Su-24 fighter jet made multiple low-level passes close to a U.S. destroyer in the Black Sea in the latest "provocation" by Moscow related to the crisis in Ukraine, Pentagon and White House officials said Monday.

The Russian Jet never flew directly over the Arleigh Burke Class destroyer Donald Cook but at one point made a pass at 500 feet within 1,000 yards of the ship, Pentagon officials said.

The Cook did not go to battle stations in the incident that lasted about 90 minutes on Saturday off Romania's coast in the Black Sea. The destroyer later docked at the Romanian port of Constanta.

The Cook was expected to remain in Constanta through Thursday and then participate in training exercises with the Romanian navy, Romanian media reported.

The incident was the latest evidence of Moscow's intentions to destabilize the region and gain sway over eastern Ukraine after annexing the Crimean peninsula, Pentagon and White House officials said.

"We've seen the Russians conduct themselves unprofessionally and in violation of international norms in Ukraine now for several months," said Army Col. Steve Warren, a Pentagon spokesman.

The incident with the Donald Cook and other "continued acts of provocation and unprofessionalism do nothing to help de-escalate the situation in Ukraine, which is what we've called on the Russians to do," Warren said.

Air Force Gen. Philip Breedlove, commander of U.S. and NATO forces in Europe, was scheduled Tuesday to provide the alliance with options for bolstering the defenses of NATO members in Eastern Europe. Breedlove's recommendations could include deploying more U.S. troops to the region and expanding military exercises.

In another sign of heightening tensions, White House Press Secretary Jay Carney confirmed that CIA Director John Brennan was in the Ukrainian capital of Kiev over the weekend to consult with authorities there on the pro-Moscow militants who have taken over government offices in eastern Ukraine.

Congressional critics of the Obama administration's response to the Ukraine crisis have repeatedly called for the sharing of intelligence on Russian activities with the struggling new government in Kiev.

Carney also said that President Obama was expected to phone Russian President Vladimir Putin to protest the Cook incident and warn of tougher economic sanctions if Russia fails to pull back the estimated 40,000 troops on Ukraine's borders.

Carney stressed that the faceoff with Russia was not intended to start a new Cold War but "we have profound differences with Russia, and we confront those differences directly."

"I can assure you that Russia's provocations and further transgressions will come with a cost," Carney said, referring to economic sanctions that are being discussed with the European Union.

"Certainly if they go further down the road in attempting to destabilize Ukraine the costs will continue to grow," Carney said.

In Ukraine, acting President Oleksandr Turchynov appeared to have backed off his Monday deadline for pro-Moscow armed groups to end their occupations of government buildings in eastern Ukraine or face an "anti-terrorist" assault by Ukrainian forces.

"Not only has that not happened, he (Turchynov) called for a national referendum on greater regional autonomy" for the pro-Moscow groups, the Kiev Post newspaper reported.

"Protesters in Kiev and elsewhere have expressed frustration at the government's reluctance to send troops to eastern Ukraine as pro-Russian forces devour large swaths of the country," the newspaper said.

In the Black Sea fly-by incident, the Russian fighter ignored repeated warnings from the Donald Cook and never responded to attempts at radio contact, Pentagon officials said.

"The Donald Cook is more than capable of defending itself" against air attack and was never under any serious threat, said Col. Warren, the Pentagon spokesman.

Warren said the jet that made runs near the Cook was accompanied by a second Su-24 Fencer that stayed at high altitude during the encounter. Neither aircraft appeared to be armed, he said.

The Cook entered the Black Sea last week amid much speculation on her mission in Russia's official media that the placement of a ship equipped with the Aegis anti-missile system was an attempt by NATO to move missile defenses closer to Russia's border.

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