WASHINGTON, Nov. 30 -- The White House said Friday that the cancellation of meeting between U.S. President Donald Trump and his Russian counterpart Vladimir Putin was because of Russia's confrontation with Ukraine, rather than the ongoing Russia probe.

The reason for the canceled meeting is Ukraine but the investigation "probably does undermine" the U.S. relationship with Russia, White House Press Secretary Sarah Sanders said in a statement.

Sanders said she hopes that the Ukraine situation "will be resolved soon so that productive conversations can begin."

A Kremlin spokesperson told Russia news outlets earlier that there will be a brief and impromptu meeting between Trump and Putin, despite the U.S. president's tweet on Thursday that their scheduled meeting in Argentina, the host of the ongoing Group of 20 (G20) summit, won't happen.

"There is no scheduled pull-aside," an anonymous White House official told U.S. media later when asked to confirm the Russian media's report.

The Ukrainian Navy said Sunday that Russian forces opened fire and seized three Ukrainian ships near the Kerch Strait, adding that six Ukrainian military sailors were wounded, two of them in serious condition.

Russian authorities said the Ukrainian ships breached the Russian border and conducted dangerous maneuvers in spite of orders of accompanying Russian vessels.

The Ukrainian Navy said that it had informed Russia in advance about the passage of Ukrainian vessels from the Black Sea to the Sea of Azov through the Kerch Strait.

The Ukrainian parliament supported a bill earlier this week imposing a martial law in certain regions for 30 days starting from Wednesday due to the tensions with Russia in the Sea of Azov.

Sanders' statement came amid a week filled with new developments in the Russia inquiry led by special counsel Robert Mueller, who was looking into the alleged Russian interference in the 2016 U.S. presidential election and any potential collusion between the Trump presidential campaign and Moscow.

Trump's former personal lawyer Michael Cohen reached a guilty plea with Mueller on Thursday to a count of making false statements to Congress about an aborted Trump Tower development project in Moscow. Cohen has been in discussions with Mueller's team, beginning in August and continuing through last week.

In response, Trump told reporters that Cohen is "a weak person" who was lying to get a reduced sentence, as he defended the legality of his business activities when he was running for the president in 2016.

"Against all odds, I decide to run for President &continue to run my business - very legal &very cool, talked about it on the campaign trail. Lightly looked at doing a building somewhere in Russia. Put up zero money, zero guarantees and didn't do the project. Witch hunt!" Trump tweeted Friday morning.

Earlier this week, embattled former Trump campaign chairman Paul Manafort was accused of repeatedly lying to investigators after pleading guilty to federal charges related to his work as an unregistered lobbyist for Ukraine -- prior to his time with the Trump campaign.

Prosecutors alleged that Manafort had breached a plea agreement that he signed in September with Mueller, but his attorneys denied that he had lied to federal investigators. Mueller is reportedly considering new charges for Manafort.

Trump has recently escalated attacks against the Mueller probe that he has frequently slammed as a "hoax" or "witch hunt." He has denied any wrongdoing or trying to shut down the investigation but has urged Mueller to wrap it up.

Russia has repeatedly denied meddling in the U.S. elections.