Disney is prepared to offer significant cash if needed, the sources said. The two are in agreement on a $52.4 billion bid for Disney to buy Fox's movie studio and other assets. But Disney is competing with a potential bid by Comcast, the parent of CNBC.
Comcast is expected to make a bid if a federal judge rules in favor of AT&T in a trial over its merger with Time Warner. Its offer is expected to top Disney's and be in all cash. Disney is preparing to counteract in the event Fox's board decides it wants cash as part of Disney's deal, which currently is all stock.
Disney is looking at whether it will add cash on top of its existing bid or simply change the composition of the bid to include cash.
Last week, Comcast said it was in "advanced stages of preparing" a superior all-cash offer for the Fox assets. But Disney's all-stock offer has been viewed more favorably because the assets could be spun off tax-free.
Liz Moyer contributed reporting