The U.S. announcement said it would favor the addition of two or three others but did not name any candidates. The statement followed months of diplomatic speculation dominated by a united proposal set out by the "Group of Four" -- Germany, India, Brazil and Japan.
Hiroyuki Hosoda, Japan's chief Cabinet secretary told the Financial Times Friday that his government was "grateful for the support" but had agreed on a plan with Germany, Brazil and India.
U.S. Undersecretary of State Nicholas Burns made it clear the United States opposed the Group of Four proposal, which he described as a "big bang expansion" that would cripple the effectiveness of the Security Council.
The four have proposed permanent seats for themselves and two African states to be decided, plus six more non-permanent members.