With his administration reeling over new reports of his campaign's Russia ties, President Donald Trump said it was President Barack Obama who lost Crimea.

Trump tweeted about about Russia's seizure of the strategically important peninsula from Ukraine in 2014 amid calls for new investigations following National Security Advisor Mike Flynn's resignation over his contacts with Russia's U.S. ambassador.

The sudden annexation occurred during Obama's second term, drawing sanctions from the U.S. and european allies, and sending U.S.-Moscow relations to a low-point from which they have yet to recover.

On Tuesday, Trump, who took heat during the campaign for his repeated praise of Vladimir Putin, asked whether his predecessor was 'soft' on Russia.

President Donald Trump asked on Twitter Wednesday whether President Obama was 'too soft on Russia'

'Crimea was TAKEN by Russia during the Obama Administration,' Trump wrote. Was Obama too soft on Russia?

He also tweeted that this 'Russian connection non-sense' is an attempt to 'cover-up' the 'many mistakes' in Hillary Clinton's losing campaign.

Trump was picking up an attack – blaming Obama for the loss of Crimea – floated by White House press secretary Sean Spicer, as he faced questions about why National Security Advisor Mike Flynn hadn't been fired sooner after his contacts with Russia's ambassador to the U.S. were first revealed.

Intercepts reportedly show the two spoke about the latest round of Russia sanctions that the Obama administration was imposing.

President Donald Trump, who praised Russian President Donald Trump during the campaign, asked whether the Obama administration was 'too soft on Russia'

Trump called the 'Russian connection' with his team 'non-sense'

Heavily-armed soldiers without identifying insignia guarding the Crimean parliament building look on as a group of men, who moments later identifed themselves as pro-Russian, approach on March 1, 2014 in Simferopol, Ukraine

A soldier under Russian command restrains a colleague after he fired his weapon into the air and screamed orders to turn back at an approaching group of over 100 unarmed Ukrainian troops at the Belbek airbase, which the Russian troops are occcupying, in Crimea on March 4, 2014 in Lubimovka, Ukraine

'The irony of this entire situation is that the president has been incredibly tough on Russia. He continues to raise the issue of Crimea, which the previous administration allowed to be seized by Russia,' Spicer said.

Last summer, during the press conference where he famously encouraged Russia to hack Hillary Clinton's emails – Trump later said he was joking – Trump fielded a question about whether he would recognize Crimea as part of Russia and lift sanctions imposed after the invasion.

'Yes. We would be looking at that,' Trump responded.

The administration's chief response to the annexation, which quickly became a de facto success after Russian-backed pro-Russia Ukrainian elements prevailed on the battlefield, was to impose a series of economic sanctions on Russia.

The U.S. also made shows of support for Russia's pro-western neighbors, sending military hardware and issuing statements reaffirming NATO's pledge to defend member states.

Unidentified masked individuals hold a Russian flag as they block the Trade Union building in Simferopol, the administrative center of Crimea, on March 1, 2014. Russia's parliament on March 1 gave President Vladimir Putin the go-ahead to send troops into Ukraine, despite a warning from Washington that such a deployment would results in "costs" for Moscow

President Barack Obama (R) shakes hands with Prime Minister of Ukraine Arseniy Yatsenyuk (L) during a bilateral meeting in the Oval Office of the White House March 12, 2014 in Washington, DC. Prime Minister Yatsenyuk was in Washington to discuss the current situation of the Russian military intervention in the Crimea area

President of the European Council Herman van Rompuy, Canadian Prime Minister Stephen Harper, French President Francois Hollande, British Prime Minster David Cameron, U.S. President Barack Obama, German Chancellor Angela Merkel, Japanese Prime Minister Shinzo Abe, Italian Prime Minister Matteo Renzi and President of the European Commission Jose Manuel Barroso attend a meeting of the G7 leaders on March 24, 2014 in The Hague, Netherlands met to develop a response after Russia annexed of the Crimea region

Early in the Obama administration, then Secretary of State Hillary Clinton tried to orchestrate a 'reset' with Russia, but the effort failed.

Maria Zakharova, spokeswoman for the Russian Foreign Ministry, was defiant when asked about Spicer's comments Wednesday.

'We don't give back our own territory. Crimea is territory belonging to the Russian Federation," she said, Reuters reported.

"The theme of returning Crimea will not be discussed,' said Kremlin spokesman Dmitry Peskov. 'Russia does not discuss its territorial integrity with foreign partners,' he said.