Ukrainian troops began training in Oklahoma on Tuesday, as top U.S. military official Gen. Mark Milley traveled to Poland, near the border with Ukraine.

Driving the news: Milley, chair of the Joint Chiefs of Staff, met with his Ukrainian counterpart, Gen. Valerii Zaluzhnyi, for the first time, signaling "unwavering support" during a critical time in Russia's war with Ukraine, per a Department of Defense spokesperson.

Meanwhile, about 90 to 100 Ukrainians were undergoing training at Fort Sill to learn to operate and maintain the Patriot missile defense system, according to the Defense Department.

• The training is set to last for several months.

The big picture: International aid to Ukraine is ramping up, with the U.S. having provided more than $24 billion in security assistance along with some 30 countries that have supplied military equipment since Russian forces first invaded the country nearly a year ago.

What we're watching: National Security Council spokesperson John Kirby told CNN Tuesday evening, "I suspect that you will continue to hear coming from the United States additional packages of security assistance, additional weapons and capabilities for Ukraine — perhaps as soon as the end of this week."

What's next: Milley, along with Secretary of Defense Lloyd Austin, was scheduled to convene another session of the Ukraine Defense Contact Group at the Ramstein Air Base in Germany on Thursday, per the Defense Department.

• "The secretary looks forward to meeting with defense leaders from the approximately 50 nations that are part of this important group dedicated to Ukraine's self-defense," Pentagon Press Secretary Air Force Brig. Gen. Pat Ryder said Tuesday.

Go deeper: Ukrainian forces begin expanded U.S. military training in Germany

Editor's note: This article has been updated with comment from National Security Council spokesperson John Kirby.