President Bush tried to make more clear his position on Iran as he arrived in Omaha on Wednesday for a fundraiser and health care tour.
Standing on the tarmac at Eppley Airfield, the president said he had been briefed by his national security team on Secretary of State Condoleezza Rice's consultations with international leaders and that the United Kingdom, Germany, France and Russia "clearly understand that the Iranian nuclear issue is a problem and continues to be a problem that must be addressed by the international community."
"It is clear from the NIE (National Intelligence Estimate) that the Iranian government has much to explain about its past activities and future intentions." Tehran, he said, faces the choice between "coming clean about the scope of its nuclear ambitions or they can continue on the path of isolation that is not in the best interests of its people."
Bush issued the stern warning as he sought to keep pressure on Iran despite a new intelligence report that Tehran halted its nuclear arms program four years ago, contradicting his earlier assertions that it was building an atom bomb.
The president insisted that Iran has not fully accounted for its nuclear activities as it continues to defy demands to halt uranium enrichment.
Bush spoke a day after he insisted that Iran remains dangerous and urged continued international pressure.
The White House said Wednesday that the United States would press ahead with its campaign for a third round of U.N. sanctions on Iran.
The shift in the intelligence community's thinking on Iran, however, was expected to stiffen resistance to further punitive measures.
"The Iranians have a strategic choice to make, they can come clean with the international community about the scope of their nuclear activities and fully accept the longstanding offer to suspend their enrichment program and come to the table and negotiate, or they can continue on a path of isolation that is not in the best interest of the Iranian people," Bush said.
"The choice is up to the Iranian regime," he added.
The president is in Nebraska in support of Mike Johanns' Senate campaign and to make a health care statement at the OneWorld Community Health Center. He was expected to return to the White House Wednesday afternoon.
Reuters contributed to this story.