Russian officials have denied U.S. allegations that Russia is preparing a “false flag” operation as pretext to invade Ukraine. In the most basic sense, false flag operations involve a country faking an attack on itself to make it appear as though said attack was carried out by an enemy.

Amid a troop buildup on the Ukrainian border, Russia has held a series of war games in regions that border Ukraine. On Monday, the military announced the launch of another exercise involving armored units, including 300 combat vehicles stationed in the western part of Russia.

German Foreign Minister Annalena Baerbock warned that “any further escalation would carry a high price for the Russian regime–economic, political and strategic” and emphasized the need to continue negotiations.

“We are prepared to have a serious dialogue with Russia, because diplomacy is the only way to defuse this highly dangerous situation,” she said.

Baerbock said Germany has offered to send cybersecurity specialists to Ukraine to help investigate last week’s cyberattacks, which Ukrainian authorities have blamed on Russia. At the same time, she noted that Germany hasn’t changed its refusal to provide it with weapons.

Russian diplomats have insisted during recent talks that they had no plans to invade but repeatedly warned that a very dangerous situation would ensue if the U.S. and NATO refused to accept its security demands. Washington and its allies firmly rejected Moscow’s demands during last week’s Russia-U.S. negotiations in Geneva and a related NATO-Russia meeting in Brussels.

Russian President Vladimir Putin has also warned that Moscow will take unspecified “military-technical measures” if the West stonewalls its demands.

Russia annexed the Crimean Peninsula from Ukraine in 2014 after the ouster of Ukraine’s Moscow-friendly leader and also threw its weight behind a separatist insurgency in eastern Ukraine. More than 14,000 people have been killed in nearly eight years of fighting there. Some believe a similar playbook was used to give Russia a pretext for invasion.