What is the source of tensions between Russia and Ukraine?

Ukrainian and Western officials are worried that a Russian military buildup near Ukraine could signal plans by Moscow to invade its ex-Soviet neighbor.

The Kremlin insists it has no such intention and has accused Ukraine and its Western backers of making the claims to cover up their own allegedly aggressive designs.

It’s unclear whether the Russian troop concentration heralds an imminent attack. The buildup could be an attempt to back up Russian President Vladimir Putin’s demand for Western guarantees prohibiting NATO’s expansion into Ukraine.

FULL COVERAGE: UKRAINE AND RUSSIAN TENSIONS \s– Biden, Putin square off as tension grows on Ukraine border \s– Ukraine: Russia sends troops to war-torn east amid tensions \s– Beyond Ukraine, plenty of issues for Biden-Putin talks
Here is a look at the current tensions:

WHAT ARE THE ROOTS OF THE RUSSIA-UKRAINE STANDOFF?

Ukraine, which was part of the Russian empire for centuries before becoming a Soviet republic, won independence as the USSR broke up in 1991. The country is working to break free from its Russian imperial past and forge closer ties with the West.

Viktor Yanukovych, a pro-Kremlin Ukrainian president, rejected an association agreement with the EU in favor of closer ties with Moscow, sparking mass protests that led to his ouster in 2014. Russia responded by annexing Ukraine’s Crimean Peninsula and throwing its weight behind a separatist insurgency that broke out in Ukraine’s east.

Ukraine and the West accused Russia of sending its troops and weapons to back the rebels. Moscow denied that, charging that Russians who joined the separatists were volunteers.

The battle in Ukraine’s eastern industrial heartland, known as Donbas, has claimed the lives of over 14,000 people.

Large-scale conflicts were assisted to cease by a 2015 peace accord signed by France and Germany, but efforts to reach a political settlement have failed, and isolated clashes have occurred along the sensitive line of contact.

A spike in cease-fire breaches in the east and a Russian army concentration near Ukraine sparked war worries earlier this year, but tensions eased as Moscow withdrew the majority of its units after maneuvers in April.

THE MOST RECENT RUSSIAN MILITARY STRUCTURE

Last week, US intelligence authorities assessed that Russia is planning to deploy an estimated 175,000 troops, with over half of them already stationed near Ukraine’s border in preparation for an invasion that could begin as early as early 2022.

Following extensive war games in western Russia in the fall, Ukraine has protested that Moscow has stationed nearly 90,000 troops near the two nations’ border.

The Russian 41st army has remained around Yelnya, a town some 260 kilometers (160 miles) north of the Ukrainian border, according to the Ukrainian Defense Ministry.

The number of Russian troops near Ukraine and in Russian-annexed Crimea is believed to be 94,300, according to Ukrainian Defense Minister Oleksii Reznikov, who warned that a “large-scale escalation” is conceivable in January.

Furthermore, the commander-in-chief of the Ukrainian armed forces claims that Russia has roughly 2,100 military men in Ukraine’s rebel-controlled east and that Russian officers command all separatist forces. Moscow has denied that its forces are stationed in eastern Ukraine on several occasions.

Russia has remained tight-lipped regarding its soldier numbers and placements, claiming that their presence on its own soil should not be a source of concern.

WHAT ARE THE DESIRES OF MOSCOW?

The Kremlin has accused Ukraine of breaking the 2015 peace agreement and has chastised the West for failing to persuade Ukraine to comply. The accord was a diplomatic success for Moscow, as it required Ukraine to allow insurgent territories broad autonomy and grant the rebels a broad amnesty.

Despite the Kremlin’s denials, Ukraine has referred to cease-fire violations by Russia-backed separatists and claims that Russian troops remain in the insurgent east.

In the midst of the recriminations, Russia has refused a four-way meeting with Ukraine, France, and Germany, claiming that it would be futile given Ukraine’s failure to comply with the 2015 deal.

Moscow has slammed the US and its NATO partners for arming Ukraine and undertaking joint drills, claiming that this encourages Ukrainian hawks to use force to retake rebel-held territory.

A military attempt by Ukraine to regain the east, Putin warned earlier this year, would have “severe consequences for Ukrainian sovereignty.”

The Russian president has referred to Russians and Ukrainians as “one people” and says that Ukraine was given historic Russian regions unfairly during the Soviet era.

Putin has made it clear that Ukraine’s desire to join NATO is a red line for Moscow, and he has expressed alarm over NATO nations’ ambitions to establish military training camps in Ukraine. He claimed that this would provide them a military foothold in Ukraine even if Ukraine did not join NATO.

Last week, Putin stated that Russia will seek from the US and its allies “solid and long-term security guarantees” that “would prohibit any further NATO movements eastward and the deployment of weapons systems that endanger us in close proximity to Russian territory.”

He said that “threats are rising on our western border,” with NATO bringing its military facilities closer to Russia, and he offered the West real negotiations on the matter, saying that Moscow would require more than just verbal pledges, but “legal guarantees.”

Putin’s foreign affairs adviser, Yuri Ushakov, claimed Putin will press for these assurances during a video conversation with US President Joe Biden scheduled for Tuesday, but veteran US and NATO diplomats said such a demand from Russia to Biden would be a nonstarter. On Friday, Biden stated that he “doesn’t accept anyone’s red line.”

IS THE RISK OF A RUSSIAN INVASION ACTUAL?

Russia dismissed suggestions of an invasion strategy as a Western smear campaign, accusing the accusations of concealing a Ukrainian plan to assault the country’s east. Such proposals are vehemently denied by Ukraine.

Some analysts see Putin’s troop surge as a sign that he is willing to escalate the stakes in order to persuade NATO to respect Moscow’s red lines and cease deploying troops and weapons to Ukraine.

Last month, Putin expressed his delight that Moscow’s warnings have gained momentum and caused “some stress” in the West. “It’s vital to keep them in that position for as long as possible so that they don’t think of staging some unnecessary battle on our western borders,” he continued.

Officials from the United States acknowledged that Moscow’s goals remain unclear, but they cited Russia’s previous behavior as a cause for concern.

Biden promised on Friday that his administration would make it “very, very difficult” for Putin to attack Ukraine, announcing a slew of new steps aimed at deterring Russian aggression.