President Bush says Iran must understand that the international community is serious about preventing the country from developing nuclear weapons.

"It's very important for the Iranian government to hear that we are concerned about their desires," said President Bush. "And we are concerned about reports that show that prior to a certain international meeting they are willing to speed-up processing of materials that could lead to a nuclear weapon. This is a very serious matter. The world knows it is a serious matter, and we are working together to solve this matter.

President Bush was referring to reports that Iran is producing a precursor to enriched uranium ahead of a meeting of the International Atomic Energy Agency in Vienna next Thursday.

The U.S. State Department has said that, if reports are true that Iran is making uranium hexafluoride gas - which is used to enrich uranium for nuclear reactors or atomic bombs - that would further erode Tehran's credibility.

The United States wants the IAEA meeting to refer Iran's case to the U.N. Security Council for possible economic sanctions.

Iran is trying to avoid those sanctions and last Sunday agreed to suspend all uranium enrichment activities in a deal negotiated by Britain, France, and Germany.

Speaking to reporters following a meeting with Japanese Prime Minister Junichiro Koizumi, President Bush said he appreciates the efforts of Britain, France, and Germany to convince Iran to give up its nuclear ambitions. He says that involvement shows that those countries, and many others, believe that Tehran has those ambitions and is moving forward to fulfill them.

The IAEA has inspectors in Iran ready to verify the suspension of uranium enrichment, which Tehran says will begin Monday.

Iran says its nuclear program is a civilian effort to produce electricity. The Bush administration says the oil-rich country has no need for nuclear energy and believes Iran's nuclear program is part of a clandestine effort to develop nuclear weapons.