Rather than watch silently, senior Bush administration officials began urging nations in the area to deny the plane the right to fly over their territory. China and at least one Central Asian nation cooperated, according to senior officials, who confirmed the outlines of the incident to demonstrate that President Bush's strategy to curb proliferation, which has been criticized by some experts for moving too slowly, is showing results. The officials insisted on anonymity because they were discussing sensitive information.

The officials said they believed the Iranian plane left without its cargo, but they were not sure. Nonetheless, the new effort underscored the efforts the administration is undertaking to curb the North's exports of missile parts, drugs and counterfeit currency that are widely believed to be its main source of revenue and the way it finances its nuclear program.

In interviews, the officials insisted that the more aggressive tactics would enhance the effort by the United States to continue negotiations over disarming North Korea, which have lasted for two years and resulted last month in a statement of broad principles to disarm, but no agreement about when or how.

"We are taking a number of new steps - defensive measures - that are intended to provide protection against all aspects of the North Korean proliferation threat," said Robert Joseph, the undersecretary of state for arms control and international security, who has been visiting former Soviet republics and other nations to secure commitments to halt flights like the one in June.

"These measures are necessary for our defense and the defense of our friends and allies," said Mr. Joseph, regarded as an administration hawk on North Korea. He also said the measures "are independent of the diplomatic efforts that we are pursuing" with the North that also include China, Russia, Japan and South Korea. "We believe that they will reinforce the prospect for the success of those talks."

But the Asian allies are divided on that question. South Korea's government, which is preparing for a visit by Mr. Bush next month, has been privately warning against taking steps that would aggravate North Korea. Arguing that "status quo isn't working," one senior administration official said this weekend that "we have to defend against illicit activity that harms America."

Russia has expressed similar concerns about pressuring Iran, saying that such action may force Tehran to show its defiance by resuming the enrichment of uranium.

On Sunday evening, Stephen J. Hadley, the president's national security adviser, arrived here to meet President Vladimir V. Putin and a range of Russian national security officials. The American efforts to exert more pressure on both North Korea and Iran - questions on which Moscow and Washington have been deeply divided - are expected to figure in his discussions.

Mr. Hadley is the second high-level administration official to arrive here in the past 10 days. Earlier this month, Secretary of State Condoleezza Rice was here on a similar mission, though when she left, Russian officials said they were still opposed to any step that would refer Iran to the United Nations Security Council for sanctions. For Russia, it is a matter of business as well as politics: Moscow is selling Iran the technology for a civilian nuclear reactor.

The new administration effort has three components, according to Mr. Joseph and other officials. The first is to block the sale of any bomb material or radioactive material from North Korea. The second is to beef up anti-proliferation efforts, including denying overflight rights.

Mr. Joseph recently visited Turkmenistan, Tajikistan, Kyrgistan and Kazakhstan, urging them to join a program called the Proliferation Security Initiative, which began as an effort to seize equipment at sea - like the BBC China, a freighter filled with centrifuge parts bound for Libya that was seized two years ago.

"We were inspired by the June incident," one senior official said this weekend, "and we said, 'Let's be more systematic.' "

A third component of the effort is to step up "counterproliferation," which involves preparing nations to counter chemical or biological weapons, and work out ways to defend against a missile attack. Japan, which has grown more hawkish on North Korea, has said it will join the American missile defense program, basing its anti-missile system on ships offshore. South Korea has declined, though it has long made use of the American-made Patriot system against short-range missiles.

One administration official cautioned that "some of these programs are new descriptions of older efforts, with more money in the pot."

But while the administration has been taking steps to isolate North Korea since President Bush took office in 2001, the combination of the effort to deny overflight rights to the Iranian plane and other recent activities suggests that the effort is being reinvigorated. It is being spurred, officials say, by some in the administration who suspect the North's willingness to sign a "statement of principles" to give up its weapons was a stalling tactic. So, using a series of exisiting powers and a new executive order signed by President Bush, the Treasury Department charged a bank based in Macao, Banco Delta Asia, with money-laundering, saying it was aiding North Korea's black-market dealings. The bank has denied the charge.

This summer, American officials seized $2 million in counterfeit bills, which it said were produced in the North, and a man linked to the Irish Republican Army was arrested in Belfast, charged with trafficking in fake currency produced in the North.