Israel Matzav

But the ranks of reformists in Iran have been depleted. Many activists are angry at the Obama administration for failing to support them six years ago in a rebuff that hasn’t been previously reported.

Iranian opposition leaders secretly reached out to the White House in the summer of 2009 to gauge Mr. Obama’s support for their “green revolution,” which drew millions of people to protest the allegedly fraudulent re-election of President Mahmoud Ahmadinejad. 

The demonstrations caught the White House off guard, said current and former U.S. officials who worked on Iran in the Obama administration. 

Some U.S. officials pressed Mr. Obama to publicly back the fledgling Green Movement, arguing in Oval Office meetings that it marked the most important democratic opening since the 1979 Islamic revolution. 

Mr. Obama wasn’t convinced. “‘Let’s give it a few days,’ was the answer,” said a senior U.S. official present at some of the White House meetings. “It was made clear: ‘We should monitor, but do nothing.’ ” 

The president was invested heavily in developing a secret diplomatic outreach to Mr. Khamenei that year, sending two letters to the supreme leader in the months before the disputed election of Mr. Ahmadinejad, said current and former U.S. officials.