President Biden will announce during Ukrainian President Volodymyr Zelensky‘s planned visit to Washington Wednesday that the U.S. will provide Ukraine with a Patriot missile defense battery, according to a senior administration official.

Why it matters: While the U.S. and its allies, including France and Germany, have provided various missile defense systems to Ukraine in recent weeks, the Patriot system will be the most advanced sent to the country since the war began.

• Ukraine has been pressing its partners for air defense systems, especially the sophisticated Patriot battery, to guard against Russian attacks on civilian infrastructure, including the electric grid in Kyiv and other cities.

Driving the news: Zelensky's trip to Washington is his first outside of Ukraine since the invasion began. He will meet with Biden, hold a press conference, and then address a joint session of Congress — all within "a few short hours" before returning to Ukraine, the administration official told reporters.

• The U.S. official said Biden will announce a $2 billion assistance package, including the Patriot battery, during Zelensky's visit, which will fall on the 300th day of the war.
• Congress is poised to pass $45 billion in additional military and economic aid to Ukraine this week as part of its $1.7 trillion omnibus spending bill, bringing total U.S. assistance to over $100 billion. The U.S. official said Zelensky's visit would help build "momentum" for additional assistance from the U.S. and its allies.
• The planned D.C. visit will come a day after Zelensky took an unexpected trip to Bakhmut, a town near the frontlines in Donetsk that has been the focus of intense fighting between Russia and Ukraine in recent weeks.

Details: With its sophisticated radar and missile interceptors, the Patriot system can be used to shoot down targets like aircraft and ballistic missiles.

• Each launcher in the Patriot system can hold four missiles, and a typical battery includes up to eight launchers. The system requires dozens of soldiers to operate.
• The U.S. will also provide precision-guided bombs in the latest package, per AP.

The U.S. will send the Patriot battery to a third country, where Ukrainian forces will be trained to use it before it's transferred to Ukraine, the senior administration official said.

• According to CNN, which was first to report the plan, the training will take place at a base in Germany and could take several months.
• Prior to the announcement, Moscow warned of "consequences" if the U.S. provided Patriots to Ukraine.

Worth noting: Asked if Biden would push Zelensky to seek diplomacy with Russia, the senior official said the visit was not about "pushing or prodding or poking" Zelensky, but about showing support and solidarity.

This is a developing story. Please check back for updates.