London ? John Bolton, America’s ambassador to the United Nations, predicted Friday that efforts to greatly expand the Security Council will fail.

Bolton’s remarks were a rare case of a U.S. official publicly speculating on the outcome of a bitter Security Council reform debate. In the past, he and other officials have repeated strong American opposition to rival proposals for adding at least 10 seats to the 15-nation body.

Bolton, who has made overhauling the United Nations a priority since President Bush appointed him to the job, said the world body must become more efficient, effective and accountable. Making the Security Council too large would undermine that goal, he said.

Increasing the number of seats to 25 or 26 “gives us great pause,” he said, adding that the maximum that Washington could support would be 19 or 20 seats.

U.S. opposition is a key factor because there is no consensus among the 191 U.N. member states on how to expand the council. Also, while the United States does not have the power to block a vote in the General Assembly, where there are no vetoes, its support would be crucial when necessary changes to the U.N. Charter would have to be approved by national legislatures.