When Barack Obama ran for president in 2008, he said he wanted to engage in constructive talks with Iran. He sought to show a contrast with President George W. Bush in establishing lines to Cuba, North Korea, and other nations hostile to the United States.

The recent rejection by Iran’s Ayatollah Ali Khamenei of one-on-one dialogue with the United States is the latest evidence of the limits of Mr. Obama’s policy. The administration’s decision to place Iran’s nuclear capacity at the top of its list of objectives was understandable but unsubtle, prompting Iranian suspicion.

In his first term, both the President and his then-secretary of State, Hillary Clinton, had political ambitions — Mr. Obama for re-election in 2012 and Mrs. Clinton for another possible presidential run in 2016. That made both of those officials unwilling to risk the failure that highly visible initiatives, such as traveling to Tehran, could have led to.

Iran’s chaotic political situation also obstructed the effort to establish a dialogue with the United States. Mr. Khamenei and his coterie continue to scrap with Iranian President Mahmoud Ahmadinejad and his allies.

Iran’s more realistic technocrats had hinted at, and perhaps even set up, a meeting with the Americans. But the supreme leader has quelled that effort, whether out of profound suspicion of dealing with the United States or an attempt to reinforce his power.

This development constitutes a failure for both countries. Iran and the United States need stronger, more determined leadership to arrive at constructive talks.

First Published February 15, 2013, 6:13 a.m.