Russia still does not plan to invade Eastern Ukraine, the Russian ambassador to the United States reiterated to ABC News' George Stephanopoulos during an appearance on "This Week" Sunday.

But despite Ambassador Sergey Kislyak's insistence, U.S. officials remain concerned about the tens of thousands of Russian troops massing on the Ukrainian border, who Kislyak said are simply there for training exercises.

"We have said so many times that we have no intent, no interest in crossing the border," Kislyak said on "This Week." "We have our forces conducting the exercises in the territory of the Russian Federation. That is normal exercises that we are conducting."

As for whether Russia would consider pulling back from the breakaway region of Crimea, Kislyak said that the area's annexation back into the former Soviet orbit was already a done deal.

"What kind of pullback from Crimea are you talking about? We are now in the area of the Russian Federation. One has to be very realistic about it," he said.

Kislyak also responded to efforts by President Obama to dress Russia down, with Obama saying at a press conference last week that "Russia is a regional power that is threatening some of its immediate neighbors - not out of strength, but out of weakness."

"If you consider Russia a regional power, look at the region we are in," Kislyak responded. "It's from Europe to Asia. It's quite a significant region in the first place."

As Secretary of State John Kerry meets with Russian Foreign Minister Sergey Lavrov in Paris to discuss a diplomatic solution, Kislyak said he was hopeful both sides could reach an agreement that gives Russian-speaking regions of Ukraine greater autonomy.

"It's a country that certainly needs a revision of the constitution that would include a mechanism where the regions would be heard and the views will be taken on board," Kislyak said.

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