Biden has pushed for supplemental aid, and he doesn’t have to. He can signal that he’ll veto any additional aid. He can certainly put pressure on Democrats to repeal already-appropriated aid, and he’d even pick up a number of Republicans on that. I also seem to remember a thing where Trump was blocking delivery of approved aid to Ukraine (with the illegal part being that it was for a quid-pro-quo), so stopping aid is certainly possible for a president.
But instead he’s pushing for more aid to Israel’s military. So once again, performative.