By Hannah Lang and Tom Wilson WASHINGTON/LONDON (Reuters) -Crypto giant Binance signed a nonbinding agreement to buy rival FTX’s non-U.S. unit, FTX.com, to help cover a “liquidity crunch” at the cryptocurrency exchange, in a surprise move that lifted cryptocurrencies on Tuesday. Binance CEO Changpeng Zhao said in a tweet that FTX, run by billionaire Sam Bankman-Fried, had “asked for our help” after “a significant liquidity crunch.” He said Binance, the world’s biggest crypto exchange, will be conducting due diligence in the coming days as the next step toward an acquisition of FTX.com. The U.S…