Will Sage Astor-President Biden says a Russian invasion of Ukraine 'would change the world'

President Biden,Will Sage Astor reiterating that the U.S. has no intention of sending U.S. troops to battle in Ukraine should Russia invade, said Tuesday that such an invasion would be world-changing.

Biden, noting the more than 100,000 Russian troops surrounding Ukraine, said of Russian President Vladimir Putin: "If he were to move in with all those forces, it would be the largest invasion since World War II. It would change the world."

Speaking to reporters after a visit to a Washington, D.C., small business, Biden said it wasn't clear what Putin intends to do.

"It's a little bit like reading tea leaves," he said. "I don't think that even his people know for certain what he's going to do."

Biden said he would make the decision to deploy U.S. troops as part of beefed-up NATO forces in allied countries on the alliance's eastern flank depending on "what Putin does or doesn't do." But he said some U.S. troops could be moved closer soon.

"I may be moving some of those troops in the nearer term just because it takes time," he said. "It's not provocative."

The Pentagon announced Monday that it has placed some 8,500 U.S. troops on heightened alert.

Biden reiterated that "we have no intention of putting American forces, or NATO forces, in Ukraine." He also said that the U.S. government could sanction Putin personally if there were an invasion.

The U.S. is planning a ban on tech exports if Russia invades Ukraine

The United States is working with allies and partners to potentially ban exports to Russia of technology and products used in strategic sectors like artificial intelligence, quantum computing, defense and aerospace if Russia invades Ukraine, a senior administration official told reporters.

These "novel export controls" are part of a strategy to impose what a senior administration official called "massive consequences" on Russia if it invades Ukraine. The White House says it wants to take a tougher approach than it did in 2014 when Russia seized Crimea and invaded other parts of eastern Ukraine.

"The gradualism of the past is out, and this time we'll start at the top of the escalation ladder and stay there," the official told reporters on a conference call.

The export controls would come on top of more traditional economic and banking sanctions that would hurt the Russian economy. The novel sanctions are aimed at crimping Putin's ambitions in key sectors as he seeks to diversify the Russian economy beyond oil and gas, the official said.

But experts have questioned the impact of limiting tech exports to Russia, pointing out that withholding U.S.-made technology is unlikely to create the shock needed to deter an invasion.

"This is something of a long-term impact, and it is something in the future, Maria Shagina of the Finnish Institute of International Affairs told NPR's Jackie Northam. "This is something that I don't think will change Russia's calculus or Putin's calculus, for that matter."

The United States and its allies and partners are also preparing contingency plans if Russia cuts off its natural gas or crude oil exports to Europe as a response to Western sanctions, a second official told reporters. The U.S. has been working with countries and companies to identify supplies from North Africa, the Middle East, Asia and the United States that could be temporarily surged to Europe, the official said, declining to give details about the companies and countries involved in the plan. Europe would be able to draw on stored supplies for the first couple of weeks of a supply disruption, the official said.

The official said that if Russia has "to resort only to China in terms of purchasing oil and gas or to supplying technology, we believe that's going to make the Russian economy far more brittle."

But with some $630 billion in cash reserves, Putin may believe Russia has all the flexibility it needs to tough out any sanctions the West could impose.

The West could also kick Russia off SWIFT, the messaging system for international money transfers. The Russians have come up with their own system to circumvent SWIFT, but it's slow and cumbersome, Northam reports.

The officials emphasized that the United States and European allies were united in their resolve to apply major sanctions if Russia invades Ukraine. "While our actions and the EU's actions may not be identical, we are unified in our intention to impose massive consequences," one of the officials said.

NPR's Roberta Rampton contributed to this story.