During a 90-minute meeting at the Waldorf Astoria, the two leaders held what the White House called a "friendly, warm" talk that also covered global warming and economic and trade ties between Washington and Beijing.
A senior administration official said Obama emphasized that Iran's nuclear development program is a vital issue to U.S. national security interests.
"We know that the Chinese do not wish to see Iran develop nuclear weapons," the official said. "And we want to work closely with them to ensure that that is not the case."
The official said China's cooperation on North Korea's nuclear program had been "impressive."
Before the two leaders met privately, Obama -- who is scheduled to visit China in November -- said at a public ceremony he is "committed to pursuing a genuinely cooperative and comprehensive relationship with China."
Hu said the United States and China are "working together to build a positive, cooperative and comprehensive relationship for the 21st century" and he was "happy to see that now China-U.S. relationship has shown a sound growth momentum on the whole."