LAS VEGAS — Former President George W. Bush said the United States must show that it can follow through on its promises, and argued against the lifting of sanctions against Iran during rare remarks about foreign policy in a meeting with hundreds of Jewish donors here Saturday night.

Mr. Bush told the 700 donors attending a closed-door Republican Jewish Coalition spring meeting that he would not criticize President Obama, whose aim to degrade and ultimately destroy the Islamic State he applauded. But the former president nevertheless offered comments that many in the audience viewed as a tacit critique of his successor.

Mr. Bush voiced skepticism about the Obama administration’s pursuit of a nuclear deal with Iran. Although he had begun the diplomatic effort to press Iran to give up its nuclear program, Mr. Bush questioned whether it was wise to lift sanctions against Tehran when the Islamic government seemed to be caving in, and suggested that the United States risked losing leverage if it did so.

The former president, in an expansive mood, also offered his views on Hillary Rodham Clinton, President Vladimir V. Putin of Russia, the joy his grandchild had brought him and the difficulty his younger brother Jeb would face as a 2016 presidential candidate because of his famous last name. The New York Times received accounts of the president’s remarks from a dozen people who attended the meeting.