• President Joe Biden cast a potential Russian invasion of Ukraine in stark historical terms Tuesday, saying, "it would be the largest invasion since World War II."
• Biden's remarks reflect a growing consensus among NATO allies that any conflict in Ukraine is unlikely to be confined to a small area or a short window of time.
• Biden made the remarks during a surprise visit to Honey Made, a newly opened gift store near the Capitol that sells handmade crafts.

WASHINGTON -- President Joe Biden cast a potential Russian invasion of Ukraine in stark historical terms Tuesday, saying, "it would be the largest invasion since World War II."

"It would change the world," said Biden, if the tens of thousands of Russian troops who have been amassing on the Russian-Ukrainian border were to launch an incursion into Ukrainian territory.

Biden's remarks reflect a growing consensus among experts that any conflict in Ukraine is unlikely to be confined to a small area or a short window of time, and that its effects will ripple through Europe and beyond.

This is very different from the 2014 Russian annexation of Crimea, which was largely contained within Crimea itself, with fighting lasting a little over a month, and Ukraine ultimately withdrawing its troops.

Biden made the remarks during a surprise visit to Honey Made, a newly opened gift store near the Capitol that sells handmade crafts. The stop was part of a broader effort to highlight a rise in the number of small businesses created during the pandemic.

Russian President Vladimir Putin has been building up Russia's military presence on the Ukrainian border for months. Putin insists that Russia is only protecting itself from what he sees as an expanding NATO alliance. He wants assurances that Ukraine will not be admitted as a member.

Now, with more than 100,000 Russian troops and armaments in place, analysts and policymakers say it is unlikely that even the frantic diplomatic talks underway in Geneva between Moscow and NATO members can stop Putin from breaching Ukraine's territory.

Biden has repeatedly pledged not to send American or NATO troops into Ukraine. But he recently directed the Pentagon to ready 8,500 U.S. soldiers for potential deployments to NATO allied countries in Eastern Europe.

Asked whether the odds of a Russian invasion had increased or decreased in recent days, Biden said it was difficult to predict Putin's next move.

"It's a little bit like reading tea leaves," said Biden. "Ordinarily, with a different leader, the fact that he continues to build forces along Ukraine's border from Belarus all the way around, you'd say, 'well, that looks like he's going to do something.'"

In Putin's case, however, the autocratic leader has a long record of bluffing and doublespeak. Moreover, Russia's economy is dependent on energy exports to Europe, and they would likely take a hit from economic sanctions NATO has pledged to impose in response to any attack on Ukraine.

"There will be enormous consequences if [Putin] were to go in and invade the entire country, or a lot less than that as well," said Biden.

"For Russia, not only in terms of economic consequences and political consequences but enormous consequences worldwide," he said as he prepared to buy a sweatshirt, a necklace and a mug with the face of Vice President Kamala Harris on it.

NATO's promised economic sanctions are still being negotiated, but they are believed to be unprecedented in their scale and scope, targeting Russia's elites and its defense and industrial sectors.

Biden also said Tuesday that he was willing to sanction Putin personally.

It's unclear how much that would accomplish, however. Putin publicly claims his salary of roughly $140,000 as his only source of income, and his assets as an apartment and a few vehicles.

In reality, Putin lives in a palatial home larger than Buckingham Palace, and experts believe he is worth billions of dollars, and that he uses the global shadow banking system to hide his money.

For months, the West has watched as Putin has carried out an extraordinary build-up of Russian forces and equipment at Russia's border with Ukraine.

Russian officials have repeatedly called on the U.S. to prevent an eastward expansion of NATO, the world's most powerful military alliance.

Russia has also demanded that the U.S. "shall not establish military bases" in the territories of any former Soviet states that are not already members of NATO, or "use their infrastructure for any military activities or develop bilateral military cooperation with them."

Since 2002, Ukraine has sought entry into NATO, where the group's Article 5 clause states that an attack on one member country is considered an attack on all of them.

On Tuesday, Biden said all the NATO members in the region, which include Poland, Hungary and Romania, should rest assured the alliance is ready to defend them.

"There's no reason for anyone, any member of NATO to worry whether or not we, NATO, would come to their defense," said Biden.

Ultimately, said the president, the question of what US and NATO troops do next will depend upon what Putin does.

Following the gift shop, Biden stopped for a Jeni's ice cream on his way back to the White House.

-- CNBC'S Amanda Macias contributed to this story.