Offense or defense? Russia increases troops along Ukraine border.

NATO foreign ministers warned Russia on Tuesday that any attempt to further destabilize Ukraine would be a costly mistake as concern mounts that Moscow could be preparing to invade its neighbor.

NATO is worried about a Russian buildup of heavy equipment and troops near Ukraine’s northern border, not far from Belarus. Ukraine says Russia kept about 90,000 troops in the area following massive war games in western Russia earlier this year.

Ukrainian President Volodymyr Zelensky said last week that his country’s intelligence service had uncovered plans for a Russia-backed coup d’état. Russia denied the allegation and rejected the assertion that it is planning to invade Ukraine.

“We are very concerned about the movements we’ve seen along Ukraine’s border. We know that Russia often combines those efforts with internal efforts to destabilize a country. That’s part of the playbook, and we’re looking at it very closely,” U.S. Secretary of State Antony Blinken said.

“Any renewed aggression would trigger serious consequences,” Mr. Blinken warned ahead of talks in Riga, Latvia with his counterparts in the 30-country military organization.

Russian President Vladimir Putin sternly warned NATO against deploying its troops and weapons to Ukraine, saying it represents a red line for Russia and would trigger a strong response.

Commenting on Western concerns about Russia’s alleged intention to invade Ukraine, he said that Moscow is equally worried about NATO drills near its borders.

Speaking to participants of an online investment forum, the Russian president said that NATO’s eastward expansion has threatened Moscow’s core security interests. He expressed concern that NATO could eventually use the Ukrainian territory to deploy missiles capable of reaching Russia’s command centers in just five minutes.

“The emergence of such threats represents a ‘red line’ for us,” Mr. Putin said. “I hope that common sense and responsibility for their own countries and the global community will eventually prevail.”

The United States has shared intelligence with European allies warning of a possible invasion of Ukraine. European diplomats acknowledge the Russian troop movements, but some countries have played down the threat of any imminent invasion ordered by Moscow.

German Foreign Minister Heiko Maas said the NATO ministers will “together send an unmistakable message to the Russian government: NATO’s support for Ukraine is unbroken and its independence, territorial integrity, and sovereignty are not up for discussion.”

“Russia would have to pay a high price for any form of aggression,” Mr. Maas said. “Honest and sustainable de-escalation steps, which can only go via the route of talks, are all the more important now. I will not tire of stressing that the door to such talks is still open to Russia.”

Russia annexed Ukraine’s Crimean Peninsula in 2014 after the country’s Moscow-friendly president was driven from power by mass protests. Weeks later, Russia threw its weight behind a separatist insurgency that broke out in Ukraine’s east.

Ukraine and the West have accused Russia of sending its troops and weapons to back the rebels. Moscow denied that, saying that Russians who joined the separatists were volunteers. More than 14,000 people have died in the fighting, which also has devastated Ukraine’s eastern industrial heartland, known as Donbas.

A 2015 peace agreement brokered by France and Germany helped end large-scale battles, but efforts to reach a political settlement have failed and sporadic skirmishes have continued along the tense line of contact. Russia has refused recent overtures for talks with France and Germany.

British Foreign Secretary Liz Truss said the NATO ministers will send a message of support to Ukraine.

“We have seen this playbook from the Kremlin before when Russia falsely claimed its illegal annexation of Crimea was a response to NATO aggression. NATO is an alliance forged on the principle of defense, not provocation. Any suggestion that NATO is provoking the Russians is clearly false. Any action by Russia to undermine the freedom and democracy that our partners enjoy would be a strategic mistake,” Ms. Truss said in a statement.

Russian Foreign Minister Sergey Lavrov said it is NATO that threatens peace in the region.

“Significant units and military equipment of NATO countries, including the U.S. and Britain, are being deployed closer to our borders,” Mr. Lavrov said during a news conference in Moscow. He alleged that the West has long provoked Ukraine “into anti-Russian actions.”

Whatever Russia’s intentions, NATO would not be able to provide Ukraine with any substantial military support in time to make a difference against Russian forces, so economic measures like Western sanctions are more likely to be used to inflict a financial cost on Moscow.

NATO Secretary General Jens Stoltenberg, who is chairing the meeting in Latvia, underlined that Ukraine does not belong to the military organization so it cannot benefit from the collective security guarantee available to member countries.

“We have different options, and we have demonstrated over the years in reaction to Russia’s previous use of military force against Ukraine that we can sustain heavy economic and financial sanctions, political sanctions,” Mr. Stoltenberg said.

Meanwhile, Belarusian Defense Minister Viktor Khrenin announced that Belarus will conduct joint military drills with Russia “to cover the southern borders,” a reference to the border area near Ukraine, according to Belarus state news agency Belta.

Mr. Khrenin did not say when the exercises would take place but noted that they won’t be as large-scale as the joint drills Belarus and Russia held in September.

This story was reported by The Associated Press. Lorne Cook reported from Brussels. Dasha Litvinova and Vladimir Isachenkov in Moscow, Geir Moulson in Berlin, and Jill Lawless in London contributed.