Can they keep a "balance" in their favor until infinity?

Can they artificially keep the price at 50k with their cuckbucks?

If US gov has X amount of #bitcoin , and they sell it. They will generate a sell pressure, that pushes btc down. But they need btc to sell to push the price down or? But they can't only sell... But if they buy, they push the price up. How could they keep the price at 50k?