A bitter divide over who is to blame for scores of Palestinian deaths from Israeli fire at protests near Gaza’s border shifted Friday to the United Nations, where the United States vetoed a measure backed by Arab countries to protect Palestinians and condemn Israel.

Nikki R. Haley, the American ambassador to the United Nations, described the measure, a United Nations Security Council resolution drafted by Kuwait, as one-sided. She accused the measure’s authors of inexplicably absolving Hamas, the militant group that controls Gaza and organized the protests.

The United States, a permanent Security Council member with veto power, was the sole no vote on the measure, which was enough to defeat it. Ten members voted in favor and four abstained.

A separate American resolution proposed by Ms. Haley, which would have condemned Hamas for the Gaza violence, failed to gain any support from fellow Council members.