The U.S. and Europe are urging Putin to halt Russia's attack on Ukraine.

• Early Thursday local time, Russia launched an attack on Ukraine after months of building up its forces.
• According to NBC News, Kyiv, Ukraine's capital, experienced explosions.
• On Thursday, U.S. President Joe Biden will reveal additional retaliatory actions in response to the attack.

Early Thursday morning local time, Russian forces launched an attack on Ukraine, marking the devastating culmination of months of a Kremlin military buildup near its former Soviet neighbor's border.

According to NBC News, explosions were heard in Kyiv after Russian President Vladimir Putin announced a military action in Ukraine.

On Wednesday night, U.S. President Joe Biden condemned the action that he had tried to prevent through diplomacy and sanctions.

Biden stated that Putin's decision to launch a premeditated war against Ukraine will result in a catastrophic loss of life and human suffering. He announced that he would meet with G-7 leaders on Thursday to discuss the consequences that the United States and its allies and partners will impose on Russia for this unjustified aggression against global peace and security.

Even as Europe and the U.S. tried to prevent it through diplomacy during an emergency United Nations meeting Wednesday night, Putin's invasion of Ukraine culminated a prolonged buildup to an anticipated attack.

Earlier on Wednesday, a Pentagon official stated that approximately 80% of Russia's military forces gathered near Ukraine were prepared for an attack.

The official, speaking anonymously, stated that they are prepared to proceed immediately if they receive the command to do so.

Russian Putin has amassed sufficient aviation, maritime, and ground forces to execute a massive invasion, according to an official statement.

On Wednesday, Linda Thomas-Greenfield, the U.S. Ambassador to the United Nations, cautioned that Russia's actions in Ukraine might result in a global refugee crisis of unprecedented proportions.

Thomas-Greenfield stated at the United Nations that if Russia continues on its current course, it could potentially cause a new refugee crisis, one of the largest in the world today, with an estimated 5 million more people displaced by Russia's war of choice.

For months, the U.S. and its Western allies have observed a growing number of Kremlin troops amassing near Ukraine's border with Russia and Belarus. This military buildup mirrors Russia's strategy prior to its 2014 annexation of Crimea, a Black Sea peninsula, which led to global outrage and economic sanctions against Moscow.

The Russian government has stated that the deployment of its troops with advanced military equipment near Ukraine's borders is not an indication of an impending invasion.

Putin's recognition of two breakaway regions in eastern Ukraine led to the invasion.

This story is developing. Please check back for updates.