Olmert warned on Monday that Iran was much closer to mastering nuclear technology than previously thought.
"This technological threshold is nearer than we anticipated before. This is because they are already engaged very seriously in enrichment," Olmert told CNN in an interview recorded before he left Israel on Sunday for Washington.
The prime minister added that Iran was only a few months away from acquiring the technology needed for building a nuclear bomb.
"The technological threshold is very close. It can be measured in months rather than years," he said.
Meanwhile, Israel's ambassador to the US, Danny Ayalon, said Iran's nuclear program was expected to be a major issue on the agenda of Olmert's meeting with Bush, scheduled for Tuesday.
"The Iranian issue is becoming more urgent due to the acceleration of the enrichment process and due to Iran's defiance of the international community," Ayalon told The Jerusalem Post.
In his talks with Bush, Olmert is expected to present Israel's latest assessments regarding Iran's advancement in its nuclear program. Olmert will want to hear from Bush on the US's plans for dealing with Iran, and is expected to stress that Iran is not seen as an Israeli problem but rather as an issue concerning the entire international community.
The American approach favors pursuing the diplomatic channel through the UN Security Council in attempt to convince Russia and China to join - or at least not to oppose - a new resolution which will enable the imposition of sanctions on Iran under Chapter 7 of the UN charter.
If this avenue proves fruitless, the US is expected to go ahead with its "plan B," which consists of moving for sanctions against Iran without going through the UN Security Council. The administration would seek the participation of European nations as well as Japan, Canada and Australia in implementing such sanctions, without requesting other UN countries to join.