Mr. Kerry sought to bolster that position in his address, emphasizing that the United States “will oppose any effort by any group or participant in the U.N. system to arbitrarily and regularly delegitimize or isolate Israel.”

American officials are particularly concerned that a United Nations inquiry into the 2014 conflict in Gaza may be biased and could be used by critics to try to isolate Israel, politically or economically.

“Our hope is that the council will continue to shift its focus away from Israel and really focus on the bad human rights violators throughout the world,” a senior State Department official told reporters on Sunday, referring to nations like Syria and North Korea, which Mr. Kerry has singled out for its “appalling” human rights record.

For all his support of Israel, however, Mr. Kerry warned in a news conference after his speech against selective leaks of the nuclear talks, saying that could complicate unfinished negotiations. Mr. Kerry did not say specifically who he feared might reveal the details, but it seemed clear that he was referring to Mr. Netanyahu and his aides.