read in Tehran as showing how anxious Obama is for a deal. It ought to be avoided."
Abrams also said Obama had undercut his leverage with Iran by striking a diplomatic deal with Russia to try to eliminate Syrian nuclear weapons rather than launching a military strike that he appeared poised to order in late August.
"What happened with regards to Syria (suggests) that the Americans don't want any kind of military engagement, so all options are not on the table with regards to Iran," he said, saying that might make Israel more likely to strike Iran if the Jewish state thinks Washington is not engaged.
While there has been speculation of talks between the two presidents or between US Secretary of State John Kerry and Iranian Foreign Minister Jawad Zarif during the UN meetings, current and former US officials said lower-level contact might make more sense.
"That's often the way they start because you're not really sure what you're dealing with," said a third US official. "You can survive a lower-level meeting that doesn't work, but you can't survive a higher-level that doesn't work."
The United States has several potential candidates to lead the talks, including Wendy Sherman, undersecretary of state for political affairs, who currently leads US nuclear negotiations with Iran, and Bill Burns, deputy secretary of state, who is a past negotiator with Iran and a Middle East expert.
"The level and the negotiator will not be difficult to arrange ... the formal trappings, they'll figure out," said Dennis Ross, a former senior White House official under Obama now at the Washington Institute for Near East Policy think tank.
"If the decision has been made to do it, you cut through that. If they are still fencing around trying to determine how to do it, then that is an indication that there isn't quite the readiness there otherwise would appear to negotiate," he added.
Karim Sadjadpour, an Iran expert at the Carnegie Endowment for International Peace, said a genuine rapprochement between Iran and the United States was unlikely but that an Barack Obama-Hassan Rowhani handshake "could open a path toward detente."
"As long as Ayatollah