WASHINGTON — As 150,000 Russian troops menacingly hugged the border of Ukraine, Secretary of State John Kerry said not to worry — he’d received assurances from the Kremlin that it wouldn’t be an aggressor despite a Russian flag hoisted above a parliament building in the Crimean peninsula.

That massive buildup of land, air and sea forces — including on the streets of Black Sea port Sevastopol — since the ouster of Kremlin-backed president Viktor Yanukovych represents most of Russia’s western military might, but Foreign Minister Sergei Lavrov told Kerry it was just exercises that were previously scheduled. They just weren’t announced until Wednesday.

Kerry said he and Lavrov “talked at some length about the transition and the events in Ukraine and in the region.”

“And I asked specifically that Russia work with the United States and with our friends and allies in order to support Ukraine, to rebuild unity, security, and a healthy economy. And we also discussed the very tense situation in Crimea. I think it’s very important to underscore that Foreign Minister Lavrov relayed to me directly from President Putin a reaffirmation of the conversation that President Putin had over the weekend with President Obama,” Kerry continued. “And he stated that both the military exercise which has been conducted is not related to the Ukraine and was previously scheduled, but also – importantly – reaffirmed President Putin’s statement that Russia will respect the territorial integrity of Ukraine.”

“And we believe that everybody now needs to step back and avoid any kind of provocations. And we want to see in the next days ahead, obviously, that the choices Russia makes conform to this affirmation that we received today. We are also making the same point about reducing tensions in Crimea to the Ukrainians, and it is very important that the process continue in a thoughtful and respectful way,” he added.

However, Russian politicians have been asserting that intervention would be necessary if Moscow thought the well-being of Russian-speaking Ukrainians in the Crimea was somehow threatened or if Crimeans decided they’d rather be part of Russia. Leaders in Ukraine noted Russia’s statements have been trying to nudge the Crimean parliament toward a referendum on a declaration of autonomy.

“What danger to the Russians is in question? Is it the one fueled by Russian television and ‘predicted’ by politicians, who are ready to give Russian passports to Ukrainian citizens or those who put Russian flag on the top of the House of the Crimean Parliament?” Vitali Klitschko’s UDAR party said in a statement today. “An attempt to play a federalization card failed. Now the card of the loss of territorial integrity of Ukraine is being played. This cannot happen.”

Russian groups have been recruiting among the citizens of Sevastopol, in the region where about 60 percent of the inhabitants are ethnically Russian. Ukraine’s acting president Oleksandr Turchynov said Tuesday that intelligence and defense officials had met and “discussed the question of not allowing any signs of separatism and threats to Ukraine’s territorial integrity – meaning the events which have taken place in Crimea – and punishing people guilty of this.”

Kerry was asked in a press conference with German Foreign Minister Frank-Walter Steinmeier today whether the State Department had asked Russia to scale back its “planned exercises” as a good-faith gesture during this time of heightened tension.

“I don’t think that they are so long or prolonged that it is something that is going to have an impact on the events there,” the secretary of State said. Russia claimed the buildup is scheduled through March 3.

“And I think the very specific message from President Putin is one that we need to process. But as I said earlier, we will look to Russia for the choices that it makes in the next days for their confirmation of these statements. Statements are statements, words are words. We have all learned that it’s actions and the follow-on choices that make the greatest difference.”

Kerry said Lavrov also told him that he’d watched the takeover of the Crimean parliament by Russian-flag-wielders on TV, “but he disclaimed that they had anything to do with any formal Russian initiative.”

“And on the contrary, they’re concerned about it, and he expressed a concern about it,” Kerry insisted. Reports later unfolded that armed men took the airport at Simferopol.

White House press secretary Jay Carney confirmed at today’s briefing that the Kerry conversation with Lavrov was “the most recent conversation I’m aware of at a high level with the Russian government.”

When it was noted that a lot has happened since Obama spoke to Putin last week, Carney replied, “We are, obviously, in constant consultation at a variety of levels with the Russian government and others, as it relates to the unfolding events in Ukraine.”

“I think you can be assured that this is an issue that has attention at the highest level and will, as each day passes,” he added.

Obama never spoke with Yanukovych as the crisis unfolded over several months, leaving that up to the vice president, who called Yanukovych nine times over a three-month period of protests.

Defense Secretary Chuck Hagel said at NATO headquarters in Brussels that he’s “closely watching Russia’s military exercises along the Ukrainian border, which they announced, as you know, yesterday.”

“I expect Russia to be transparent about these activities. And I urge them not to take any steps that could be misinterpreted or lead to miscalculation during a very delicate time, a time of great tension,” Hagel continued.

NATO Secretary General Anders Fogh Rasmussen urged Russia “not to take any action that can escalate tension or create misunderstanding.”

The White House continued to say Thursday that they didn’t know where Yanukovych is — particularly when asked whether Russia giving safe harbor to the fugitive president is a provocative action –  but he is expected to give a defiant televised statement Friday from Russia.

Local Russian media reported that Yanukovych landed in Rostov-on-Don Thursday night accompanied by Russian warplanes, then proceeded to an estate for VIPs in the southern city.

The administration continued to tread carefully around the question of whether Yanukovych is still the legitimate president.

“As I’ve said earlier and others, Mr. Yanukovych abdicated his responsibilities when he packed up and left the capital of his country,” Carney said. “And he fled Kiev and has only been seen once, on videotape, since Saturday. You know, those actions undermined his legitimacy, and Ukraine’s lawmakers in the parliament are fulfilling their obligation to the Ukrainian people by forming a government that can tackle the pressing economic and political issues facing the country until new presidential elections can be held.”

But Kerry seemed to question Yanukovych’s legitimacy based in part on the fact that he hadn’t returned Vice President Joe Biden’s phone call.

“He voluntarily departed, and he signed an agreement, and then without signing the law that was the precondition to the implementation of the rest of the agreement, he departed and took off to parts unknown and was unavailable to those of us who were trying to reach him. The vice president of the United States had a call in to him for some 12 to 14 hours, unanswered,” Kerry said. “So I think it is clear that events have now overtaken whatever legitimacy he claimed.”

Biden did get Ukrainian Prime Minister Arseniy Yatsenyuk on the phone today “to welcome the formation of a new government in Ukraine.”

“The Vice President emphasized that this is an important opportunity not only to bring peace, stability, and unity to Ukraine, but also to restore the faith of all of the Ukrainian people in their country’s democratic institutions as they prepare for new elections in May,” the White House said in a readout of the call. “The Vice President reassured the Prime Minister that the United States will offer its full support as Ukraine undertakes the reforms necessary to return to economic health, pursue reconciliation, uphold its international obligations, and seek open and constructive relationships with all its neighbors.”