Under increasing pressure over his administration's relationship with Russia
, President Trump commented on Twitter Wednesday that the Crimea peninsula was "taken" by Russia from Ukraine under the Obama administration.
The comments mark a sharp U-turn for Trump, who had previously buoyed the Kremlin's claim on Crimea.
Russia annexed Crimea, a territory in the former Soviet republic of Ukraine, in March 2014 following tensions with its neighbor.
The White House and the Kremlin have engaged in back-and-forth commentry over Crimea in recent days. Trump's Press Secretary Sean Spicer said Tuesday: "President Trump has made it very clear that he expects the Russian government to deescalate violence in the Ukraine and return Crimea."
On Wednesday morning, Russia's Foreign Ministry spokeswoman Maria Zakharova said Russia would not return the territory.
"Crimea is part of the Russian Federation," she told reporters.
Just hours later, Trump tweeted, asking: "Was Obama too soft on Russia?"
Republican Senator John McCain, who has openly opposed Trump on many issues, responded to the tweet, agreeing that Obama was "too soft," and suggesting the US give "lethal assistance" to Ukraine and keep sanctions on Russia.
In July on the campaign trail, Trump had said that the Ukraine crisis was "more of a Europe problem
," and that the US should only step in on Crimea if European countries asked for help.
In July, Trump said Russian President Vladimir Putin wouldn't make a military move into Ukraine
-- even though the country had already done so by seizing the Crimean peninsula.
"He's not going into Ukraine, OK, just so you understand. He's not going to go into Ukraine, all right? You can mark it down. You can put it down. You can take it anywhere you want," Trump said in a July interview with ABC News' George Stephanopoulos on "This Week."
The exchange of words between the two governments come as the Trump administration tries to contain a scandal over high-level advisers in his team whom multiple officials say were in constant communication
with Russians known to US intelligence during the election campaign period.
Trump's former national security adviser Michael Flynn was forced to step down
Monday after it emerged he had discussed policy with the Russian ambassador to the US prior to his appointment.