In an interview, Mr. Pickering also contended that Mr. Obama should review the covert program against Iran — which has included computer sabotage of its nuclear facilities — to “stop anything that is peripheral, that is not buying us much time” in slowing Iran’s progress. The report itself, however, says nothing about the sabotage effort, which has been a major element of the American strategy.

Mr. Pickering, who is such a towering figure in the State Department that a major program to train young diplomats is named for him, is not the only prominent signatory of the report. Others include Lee H. Hamilton, who was a leader of the commission on the attacks of Sept. 11, 2001, and serves on Mr. Obama’s intelligence advisory board; Anne-Marie Slaughter, the director of policy planning during Mr. Obama’s first term; and Ryan C. Crocker, who served in many prominent ambassadorial positions. Former Senator Richard G. Lugar of Indiana, an early mentor to Mr. Obama in the Senate, was among the Republican signatories.

At the core of the difference in strategy are these questions: Are the increasing sanctions likely to harden Iran’s position and convince its supreme leader, Ayatollah Ali Khamenei, that the president’s real goal is overthrowing the current government? Or are they likely to convince the Iranians, eventually, that the price of continuing the country’s nuclear program is simply too high, as Mr. Obama has argued?

So far, there is plenty of evidence that the sanctions are hurting Iran, but none that they are changing the course of the country’s nuclear program. Still, the Senate Foreign Relations Committee voted this week to bolster sanctions, if necessary, and Israel has argued that the stalling of the most recent round of talks has offered only more proof that the Iranians are playing for time, seeking to expand their nuclear enrichment capacity while keeping the talks limping along.

Mr. Obama and his diplomats have insisted that the sanctions they have imposed are in support of diplomacy. A State Department spokeswoman, Jen Psaki, said in a statement that the administration was sticking with its approach.