The New York Times writes about this.
“Republicans said they couldn't approve aid [to Ukraine] without border provisions. Now they say they can't approve aid to Ukraine along with the border provisions. Today I will give them a choice,” Schumer told reporters.
The senator believes a “clean foreign aid” bill that eliminates border policy provisions will gain enough support in Congress.
The day before, President Joe Biden expressed disappointment that a bill to allocate money for arms supplies to Ukraine and on US border security would probably not even make it to a vote in the Senate.
His speech came after the Republican leadership in the US House of Representatives rejected a bill combining proposals to secure American borders and to allocate new money for arms supplies to Ukraine.