WASHINGTON — President Bush charged Thursday that Iran continues to arm and train insurgents who are killing U.S. soldiers in Iraq, and he threatened action if that continues.

At a news conference Thursday, Bush said Iran had been warned of unspecified consequences if it continued its alleged support for anti-American forces in Iraq. U.S. Ambassador to Iraq Ryan Crocker had conveyed the warning in meetings with his Iranian counterpart in Baghdad, the president said.

Bush wasn't specific, and a State Department official refused to elaborate on the warning.

Behind the scenes, however, the president's top aides have been engaged in an intensive internal debate over how to respond to Iran's support for Shiite Muslim groups in Iraq and its nuclear program. Vice President Dick Cheney several weeks ago proposed launching airstrikes at suspected training camps in Iran run by the Quds force, a special unit of the Iranian Revolutionary Guard Corps, according to two U.S. officials who are involved in Iran policy.

The debate has been accompanied by a growing drumbeat of allegations about Iranian meddling in Iraq from U.S. military officers, administration officials and administration allies outside government and in the news media. It isn't clear whether the media campaign is intended to build support for limited military action against Iran, to pressure the Iranians to curb their support for Shiite groups in Iraq or both.

Nor is it clear from the evidence the administration has presented whether Iran, which has long-standing ties to several Iraqi Shiite groups, including the Mahdi Army of radical cleric Muqtada al Sadr and the Badr Organization, which is allied with the U.S.-backed government of Prime Minister Nouri al Maliki, is a major cause of the anti-American and sectarian violence in Iraq or merely one of many. At other times, administration officials have blamed the Sunni Muslim group al Qaida in Iraq for much of the violence.

For now, however, the president appears to have settled on a policy of stepped-up military operations in Iraq aimed at the suspected Iranian networks there, combined with direct American-Iranian talks in Baghdad to try to persuade Tehran to halt its alleged meddling.

The U.S. military launched one such raid Wednesday in Baghdad's predominantly Shiite Sadr City district.

But so far that course has failed to halt what American military officials say is a flow of sophisticated roadside bombs, known as explosively formed penetrators, into Iraq. Last month they accounted for a third of the combat deaths among U.S.-led forces, according to the military.

Cheney, who's long been skeptical of diplomacy with Iran, argued for military action if hard new evidence emerges of Iran's complicity in supporting anti-American forces in Iraq; for example, catching a truckload of fighters or weapons crossing into Iraq from Iran, one official said.

The two officials spoke on condition of anonymity because they weren't authorized to talk publicly about internal government deliberations.

Secretary of State Condoleezza Rice opposes this idea, the officials said. Defense Secretary Robert Gates has stated publicly that "we think we can handle this inside the borders of Iraq."

Lea Anne McBride, a Cheney spokeswoman, said only that "the vice president is right where the president is" on Iran policy.

Bush left no doubt at his news conference that he intended to get tough with Iran.

"One of the main reasons that I asked Ambassador Crocker to meet with Iranians inside Iraq was to send the message that there will be consequences for . . . people transporting, delivering EFPs, highly sophisticated IEDs (improvised explosive devices), that kill Americans in Iraq," he said.

He also appeared to call on the Iranian people to change their government.

"My message to the Iranian people is, you can do better than this current government," he said. "You don't have to be isolated. You don't have to be in a position where you can't realize your full economic potential."

The Bush administration has launched what appears to be a coordinated campaign to pin more of Iraq's security troubles on Iran.

Last week, Lt. Gen. Raymond Odierno, the No. 2 U.S. military commander in Iraq, said Shiite militiamen had launched 73 percent of the attacks that had killed or wounded American troops in July. U.S. officials think that majority Shiite Iran is providing militiamen with EFPs, which pierce armored vehicles and explode once inside.

Last month, Brig. Gen. Kevin Bergner, a multinational force spokesman, said members of the Quds force had helped plan a January attack in the holy Shiite city of Karbala, which lead to the deaths of five American soldiers. Bergner said the military had evidence that some of the attackers had trained at Quds camps near Tehran.

Bush's efforts to pressure Iran are complicated by the fact that the leaders of U.S.-supported governments in Iraq and Afghanistan have a more nuanced view of their neighbor.

Maliki is on a three-day visit to Tehran, during which he was photographed Wednesday hand in hand with Iranian President Mahmoud Ahmadinejad. Unconfirmed media reports said Maliki had told Iranian officials they'd played a constructive role in the region.

Asked about that, Bush said he hadn't been briefed on the meeting. "Now if the signal is that Iran is constructive, I will have to have a heart-to-heart with my friend the prime minister, because I don't believe they are constructive. I don't think he in his heart of hearts thinks they're constructive either," he said.

Bush and Afghan President Hamid Karzai differed on Iran's role when they met last weekend, with Karzai saying in a TV interview that Iran was "a helper" and Bush challenging that view.

The toughening U.S. position on Iran puts Karzai and Iraqi leaders such as Maliki in a difficult spot between Iran, their longtime ally, and the United States, which is spending lives and treasure to secure their newly formed government.

A senior Iraqi official in Baghdad said the Iraqi government received regular intelligence briefings from the United States about suspected Iranian activities. He refused to discuss details, but said the American position worried him.

The United States is "becoming more focused on Iranian influence inside Iraq," said the official, who requested anonymity to discuss private talks with the Americans. "And we don't want Iraq to become a zone of conflict between Iran and the U.S."

Proposals to use force against Iran over its actions in Iraq mark a new phase in the Bush administration's long internal war over Iran policy.

Until now, some hawks within the administration — including Cheney — are said to have favored military strikes to stop Iran from furthering its suspected ambitions for nuclear weapons.

Rice has championed a diplomatic strategy, but that, too, has failed to deter Iran so far.

Patrick Clawson, an Iran specialist at the Washington Institute for Near East Policy, said a strike on the Quds camps in Iran could make the nuclear diplomacy more difficult.

Before launching such a strike, "We better be prepared to go public with very detailed and very convincing intelligence," Clawson said.

Ben Curtis/AP

The USS Enterprise passes behind a mosque Aug. 1 as it makes its way through the Suez canal. It replaced two carriers in a deployment aimed at sending a signal of strength to Iran.