WASHINGTON (AP) -- In a flurry of diplomacy across two continents, President Joe Biden met with Germany's new leader Monday and vowed the crucial Nord Stream 2 Russia-to-Germany gas pipeline will be blocked if Russia further invades Ukraine. Russia's Vladimir Putin retorted that the U.S. and its allies are the only ones talking invasion.
Putin and French President Emmanuel Macron met for more than five hours in Moscow at the same time Biden and German Chancellor Olaf Scholz spoke at the White House in efforts to defuse the crisis before armed conflict breaks out. Russia has massed thousands of troops at the Ukraine border, adding military might almost daily.
The White House has expressed increasing alarm about the prospects of war, and Biden has been looking to solidify support among European allies for economy-jarring sanctions against Russia if it attacks.
"If Russia invades, that means tanks and troops crossing the border of Ukraine again, then there will be no longer a Nord Stream 2," Biden said. "We will bring an end to it."
That would hurt Russia economically but also cause supply problems for Germany. Construction of the pipeline has been completed, but it is not yet operating.
"We are jointly ready, and all of NATO is ready," Biden said, referring to the powerful Western alliance, though Ukraine is not a member.
While Biden reiterated with certitude that the pipeline would not move forward, Scholz stressed the need to keep some ambiguity about sanctions in order to press Russia to de-escalate the crisis.
"It's necessary for Russia to understand that a lot more could happen than they've perhaps calculated with themselves,." Scholz said.
The buildup of over 100,000 Russian troops near Ukraine has fueled Western worries of a possible offensive. White House national security adviser Jake Sullivan warned Sunday that Russia could invade Ukraine "any day," triggering a conflict that would come at an "enormous human cost."
At the same time, Biden and NATO allies have made clear there are no plans for sending in troops to fight Russia on Ukraine's behalf.
Macron and Putin, during their lengthy meeting -- with a dinner that featured the choice of sturgeon or reindeer -- registered their disagreements but also emphasized a need for more talks.
Putin noted that the U.S. and NATO have ignored Moscow's demands that the alliance guarantee it will keep Ukraine and other ex-Soviet nations out, refrain from placing weapons in Ukraine and roll back alliance forces from Eastern Europe.
"We are categorically against any further NATO's expansion eastward because it poses a threat to us," Putin said. "It's not us who's advancing to NATO, it's NATO coming to us and so it's illogical to talk about Russia's aggressive behavior."
He scoffed at Western descriptions of NATO as a defensive alliance, saying sarcastically that "people of Iraq, Libya and Afghanistan have learned it from their own experience." And he threatened a wider war if Ukraine should join the alliance and perhaps try to win back Crimea, which Russia annexed in 2014.
"European countries will automatically be drawn into a military conflict with Russia," Putin said. "You will be drawn into that conflict beyond your will. There will be no winners."
Macron described the talks as "substantial, deep" with a focus on conditions that could help de-escalation.
"We tried to build converging elements," he said. "The upcoming days will be crucial and deep discussions together will be needed."
Putin signaled his readiness to continue negotiations and denied anew that Russia has any intention of invading Ukraine.
In the meantime, Biden warned "it would be wise" for Americans other than essential diplomats to leave Ukraine.
On a positive note, Putin said without elaboration that some of Macron's proposals could serve as a basis for a settlement of the conflict in eastern Ukraine, adding that they agreed to have a call after Macron's visit to Kyiv Tuesday.
Likewise, Biden said when asked if there remained an "offramp" for Russia in the standoff, "The answer is yes."
Before meeting Biden, Scholz told German media that "there will be a very high price if Ukraine is attacked militarily. And we are preparing for this very precisely and have been talking about the details for a long time." Scholz will travel to Kyiv and Moscow Feb. 14-15.
German Defense Minister Christine Lambrecht said her country would add up to 350 troops within a few days to about 500 already a part of a NATO battlegroup in Lithuania. "With this, we are strengthening our contribution to forces on NATO's eastern flank and sending a very clear signal of unity to our allies," she said.
Biden already has deployed additional U.S. troops to Poland, Romania and Germany, and a few dozen elite U.S. troops and equipment landed Sunday in southeastern Poland near the border with Ukraine, with hundreds more infantry troops of the 82nd Airborne Division set to arrive.
Britain said the U.K. was sending 350 troops to Poland to bolster NATO forces, joining 100 Royal Engineers already there.
At a news conference in Washington, U.S. Secretary of State Antony Blinken and EU foreign policy chief Josep Borrell defended the increasingly dire Western warnings that a Russian invasion may be imminent.
"This is not alarmism. This is simply the facts," Blinken said. "And the facts are that we've seen over the last few months a massive amassing of Russian forces on Ukraine's borders."
Borrell noted that "140,000 troops massed on the border is not to go to have tea."
NATO Secretary-General Jens Stoltenberg said the alliance is weighing a more permanent military presence in southeast Europe in response to Russia's "massive military deployment" near Ukraine.
"We are considering more longer-term adjustments to our posture, our presence in the eastern part of the alliance," Stoltenberg said after talks in Brussels with Polish President Andrzej Duda. "If Russia really wants less NATO close to the borders, they get the opposite."
Stoltenberg gave no details and said no final decision has been made, but the move could mirror NATO's long-term military presence in Estonia, Latvia, Lithuania and Poland, where about 5,000 troops are stationed. It would see a similar force based in Bulgaria, Romania, Hungary and Slovakia.
The aim would be only to bolster the defenses of NATO allies in the region. The troops would not cross into Ukraine should Russia invade.
Biden and Scholz also discussed contingency plans for providing gas supplies to Europe should Russia cut off supply. Europe is already dealing with liquefied natural gas supplies being sapped by a cold winter last year, a summer with little renewable energy generation and Russia delivering less than usual.
Biden asserted the U.S. and other countries could make up a "significant portion" of supplies lost should Russia move to cut off Europe.
But energy experts say replacing Russian gas would be complicated and can't be done overnight. Export terminals cost billions of dollars to build and are working at capacity in the U.S.