MONACO — An influential Saudi prince blasted the Obama administration on Sunday for what he called indecision and a loss of credibility with allies in the Middle East, saying that American efforts to secure a peace deal between Israelis and Palestinians would founder without a clear commitment from President Obama.

“We’ve seen several red lines put forward by the president, which went along and became pinkish as time grew, and eventually ended up completely white,” said Prince Turki al-Faisal, the former intelligence chief of Saudi Arabia. “When that kind of assurance comes from a leader of a country like the United States, we expect him to stand by it.” He added, “There is an issue of confidence.”

Mr. Obama has his problems, the prince said, but when a country has strong allies, “you should be able to give them the assurance that what you say is going to be what you do.” The prince no longer has any official position but has lately been providing the public expression of internal Saudi views with clear approval from the Saudi government.

The Saudis have been particularly shaken by Mr. Obama’s refusal to intervene forcefully in the Syrian civil war, especially his recent decision not to punish President Bashar al-Assad of Syria with military strikes even after evidence emerged that Mr. Assad’s government used chemical weapons on its own citizens.