"My message to Congress has been that let's see if this short-term, phase-one deal can be completed to our satisfaction," Xinhua quoted Obama as saying at a press conference.
Officials from Iran and the P5+1 group, namely Britain, China, France, Russia and the US plus Germany, will resume negotiations Nov 20 in Geneva after an initial round of talks ended last week without an agreement.
Obama urged the Congress to give an opportunity to see how serious Iran is about resolving the nuclear issue diplomatically and peacefully. "If they're not serious, we can dial those sanctions right back up," Obama said.
US Secretary of State John Kerry warned Wednesday that if Congress were to unilaterally move to raise sanctions, it could break faith with nuclear negotiations and break them apart.
Obama said the goal of his administration is to stop Iran from having nuclear weapons.
"It would be not only dangerous to us and our allies, but it would be destabilising to the entire region and could trigger a nuclear arms race that would make life much more dangerous for all of us," he said.
Obama said the sanctions that have been put in place are effective in crippling the Iranian economy and are the reason that brought Iran back to the negotiating table.
Iran's economy dropped five percent last year, its currency plummeted and it had significant problems in the day-to-day economy on the ground, according to the US president.
He said pursing a diplomatic path to solve Iran's nuclear issue would be his preference, because military options are always "difficult" and "have unintended consequences."