JERUSALEM — The American ambassador to Israel said this week that not only was America willing to use military force to stop Iran from developing nuclear weapons, but that preparations had already been made for a possible attack.

“It would be preferable to resolve this diplomatically and through the use of pressure than to use military force,” the ambassador, Dan Shapiro, said Tuesday at a meeting of the Israeli bar association. “But that doesn’t mean that option is not fully available. And not just available, but it’s ready. The necessary planning has been done to ensure that it’s ready.”

While American leaders, including President Obama and his defense secretary and chairman of the Joint Chiefs of Staff, have frequently said all options are on the table regarding Iran, the notion of specific plans being made is not something they typically talk about.

In fact, at a March speech to the American Israel Public Affairs Committee, the pro-Israel lobby, Mr. Obama warned that “loose talk of war” could actually speed Tehran’s move toward weaponization, saying “now is not the time for bluster.”