He can veto bills funding Israel and the current aid Israel is getting is through executive powers passed previously.
There are also laws on the books that disallow aid to countries with human rights violations that are easy to invoke.
Biden can also unilaterally put sanctions/tariffs on Israel.
There’s no somehow about it, he can stop funding today.
And will that do something? Almost certainly because the US is Israel’s largest supporter (by a long shot). Bebe can, of course, ignore this. However, that’d destroy Israel’s economy.