Beijing and Moscow have repeatedly vetoed U.S.-proposed sanctions against the Islamic Republic at the UN Security Council over its controversial nuclear program.
"My view is that we need to strengthen our sanctions regime," Bush told a news conference at the White House. "Of course, I will discuss this issue with Vladimir Putin as well as President Hu Jintao," Bush said.
"The first thing that these leaders have got to understand is that an Iran with a nuclear weapon would be incredibly destabilizing for the world. It's in their interests that we work collaboratively to continue to isolate that regime," he said.
The announcement came a day after a new report by the International Agency for Atomic Energy showed that Tehran is accelerating its uranium enrichment program in defiance of international demands. Bush described this as "unacceptable."
"The world has spoken and has said no nuclear weapons programs. But they're constantly ignoring the demands," Bush said.
The president said he had directed Condoleezza Rice, the U.S. Secretary of State, to work with European partners to "develop further sanctions."
In the latest show of Iran's defiance, President Mahmoud Ahmadinejad said Thursday Iran would not stop its nuclear development.
Since Iran resumed uranium enrichment in January 2006, the country has been the focus of international concerns, as some Western countries, particularly the U.S., suspect Tehran is pursuing a covert weapons program, which it has consistently denied, saying it needs nuclear power for electricity generation.
"The main task of our enemies is to prevent Iran from acquiring civilian-use nuclear technologies," Ahmadinejad said. "They wish to undermine the foundation of our government - and they will achieve their purpose if we stop even for a moment."
