force someone's hand

To push one to do something that one is not inclined to do otherwise. (The phrase alludes to a hand of playing cards.) Dave still hasn't decided where he wants to go to dinner, so I'm going to force his hand—I need to make reservations as soon as possible! I was hoping to play golf today, but the storm forced my hand, so I stayed home instead. The president is trying to force Congress's hand by threatening a veto.

Compel someone to act or speak prematurely or against his or her will. For example, He didn't want to decide just then, but the board forced his hand. This expression probably alludes to the hand (the cards) held in a game such as whist or poker, in which a player is compelled to play some card from his hand or to reveal his hand. [Mid-1800s]

COMMON If someone forces your hand, they make you do something that you are not ready to do or do not want to do. He hadn't wanted to talk publicly about the matter but said the press had forced his hand. If he hadn't made the announcement, the newspapers were going to do so anyway. The Government is very reluctant to make such a move. But the exchange markets may force its hand. Note: In card games, to force an opponent's hand means to force them to play a card earlier than they want to.