This article is by William J. Broad, Mark Mazzetti and David E. Sanger.

WASHINGTON  When President Obama stood last week with the leaders of Britain and France to denounce Iran’s construction of a secret nuclear plant, the Western powers all appeared to be on the same page.

Behind their show of unity about Iran’s clandestine efforts to manufacture nuclear fuel, however, is a continuing debate among American, European and Israeli spies about a separate component of Iran’s nuclear program: its clandestine efforts to design a nuclear warhead.

The Israelis, who have delivered veiled threats of a military strike, say they believe that Iran has restarted these “weaponization” efforts, which would mark a final step in building a nuclear weapon. The Germans say they believe that the weapons work was never halted. The French have strongly suggested that independent international inspectors have more information about the weapons work than they have made public.

Meanwhile, in closed-door discussions, American spy agencies have stood firm in their conclusion that while Iran may ultimately want a bomb, the country halted work on weapons design in 2003 and probably has not restarted that effort  a judgment first made public in a 2007 National Intelligence Estimate.