NEW YORK (Reuters) - Mohamed El-Erian, co-chief investment officer of Pimco, on Thursday put low odds on a third round of U.S. monetary stimulus unless there is a "major further deterioration" in the U.S. economic outlook.

"We would assign a low probability of this stage to QE3 given the general recognition that the forward-looking cost-benefit analysis has shifted away from the potential benefits and toward greater costs and risk," El-Erian said in a live blogging question and answer session on Reuters.com.

"Therefore, it would take a major further deterioration in the economic outlook, combined with a willingness by the Fed to take greater reputational and political risks," he said.

Pimco, which manages $1.2 trillion in assets, is home to the world's largest bond fund.

(Reporting by Daniel Bases and Jennifer Ablan; Editing by Kenneth Barry)