(This post was updated at 11:30 a.m. ET.)
President Obama on Tuesday said that he believed that Russia was "still making a series of calculations" regarding any further moves after its annexation of Crimea, but that there was no expectation of dislodging it by force from the Black Sea peninsula.
"What we can bring to bear are the legal arguments, the diplomatic arguments," he said at a joint news conference with Dutch Prime Minister Mark Rutte following a nuclear security summit in The Hague.
"It's not a done deal in the sense that the international community, by and large, is not accepting the annexation of Crimea," he said.
Regarding reports of 30,000 Russian troops massed on the border with eastern Ukraine, he called it an "act of intimidation" but said as long as they stayed on Russian soil, that was Moscow's "right" to have them there.
Obama said he though sanctions were already having an impact and that if the Kremlin decided to take further military actions, those sanctions would be expanded to include whole sectors of the Russian economy.
He said many of the countries with substantial Russian-speaking populations were NATO members and that under Article 5 of the NATO charter, an attack on one member of the alliance was considered an attack on all.
Obama also strenuously objected to suggestions that Russian speakers in Ukraine and elsewhere were threatened, thus justifying Moscow's actions.
"There has been no evidence Russian speakers have been in any way threatened," he said, adding that he rejected comparisons to Kosovo, where NATO intervened in 1998 in the face of accusations of "ethnic cleansing."
Russian President Vladimir Putin has alluded to the post-Cold War orphaning of Russian-speaking populations in former Soviet republics as justification for its actions in Crimea and its demand that Russian speakers in Ukraine be protected.
(For a look at Russian-speaking populations living on Russia's periphery, we have a closer look here.)
On Monday U.S. Air Force Gen. Philip Breedlove, a former NATO supreme allied commander in Europe, said that after Crimea, Moscow might be eyeing Moldova's mainly Russian-speaking separatist Transnistria region.
Breedlove's comments come amid concern that Russia, which has massed troops on its eastern border with Ukraine, might also make a move.
Adm. James Stavridis, also a former NATO supreme allied commander in Europe, tells NPR that he thinks both of those concerns "will trigger an enhanced level of cooperation between NATO and Ukraine in particular."
"I share Gen. Breedlove's concern, however, about the massing of troops on the eastern border of Ukraine. That is, in my view provocative and destabilizing," Stavridis tells Morning Edition.
Also on Tuesday, NATO Secretary-General Anders Fogh Rasmussen expressed his concern about the troops on the border.
"We are, as an alliance, focused on providing effective deterrence and defense," he said. "And all NATO allies can be assured of our determination to provide effective defense."
Earlier, Obama met with the leader of Russian ally Kazakhstan in an exchange that both sides said had nothing to do with the situation in Ukraine.
The Associated Press says the meeting with Kazakh President Nursultan Nazarbayev was a last-minute addition to Obama's schedule at a nuclear summit in The Hague. The two leaders had previously spoken by telephone on March 10, when the White House said it had urged Nazarbayev to play an active role in seeking a peaceful resolution of the Crimea crisis.
That meeting followed a surprise face-to-face on Monday between Russian Foreign Minister Sergei Lavrov and his Ukrainian counterpart. It was the highest-level meeting between the two countries since the Kremlin's annexation of Crimea earlier this month. Lavrov used the sit-down with Andriy Deshchytsia to reiterate Moscow's call for autonomy for Russian speakers in the border regions between the two countries.
"We set forth our vision to establish good national dialogue taking into account all residents of Ukraine," Lavrov said during a news conference in The Hague.
He also brushed off the concerns about Russia being expelled from the G-8 group of leading industrialized nations as a punishment for its military actions in Crimea, calling the move "no great tragedy."
Other members of the G-8 have agreed to scrap a July summit that was to be held in the Black Sea resort of Sochi, site of this year's Winter Olympics.
"If our Western partners think that this format has outlived itself, then so be it," Lavrov told reporters. "At the very least, we are not trying to cling on to this format."