Middle East Crisis: Russia and China Veto U.S.-Led Cease-Fire Resolution at U.N.
www.nytimes.com
The United States had vetoed three previous resolutions demanding a stop to fighting in Gaza. The measure it proposed on Friday called for an “immediate and sustained cease-fire.”

Edit: It looks like the argument here is that the US is not calling for an instant ceasefire, but instead saying that one is very important to have. China and Russia say it should be immediate. The US also tied it to hostage talks.

Another resolution is in the works to call for an immediate ceasefire, but the US is expected to veto it because they believe it could endanger hostage talks.