U.S. spy planes will soon resume surveillance flights off North Korea, following an aerial interception by MiGs from the Communist state 10 days ago, according to U.S. military sources. But policymakers have rejected the idea of sending an armed fighter escort, believing that would increase the risk of hostilities with North Korea.

Lt. Cmdr. Jeff Davis, a Pentagon spokesman, would not discuss details of the flights, but said: "We will conduct legal and lawful missions in international airspace around the world. They are innocent and non-threatening, and they will continue."

The modified Boeing 707 spy planes, which take off from Okinawa, Japan, to monitor missile launches and North Korean communications, will operate alone, according to several military and civilian sources in Washington and Seoul. "We do not want to do anything provocative. We do not want an international incident," said a top military officer. "We are not going to stop doing it. But we will do it with circumspection."

Today, a senior official in Washington said that North Korea's uranium enrichment program, which could allow the country to build nuclear weapons, is further along than previously believed. James A. Kelly, assistant secretary of state for East Asian and Pacific affairs, told the Senate Foreign Relations Committee that production of highly enriched uranium is "probably a matter of months, not years," behind North Korea's efforts to produce plutonium from spent nuclear fuel rods, which it plans to do within six months.

"The enriched uranium issue, some have assumed, is somewhere off in the fog of the distant future," he said. "It is not."

North Korea stunned the Bush administration in October by revealing that it had been secretly pursuing a program to produce highly enriched uranium.

In recent months, North Korea has taken a series of steps escalating the dispute with the United States -- restarting a small reactor, test-firing short-range missiles and threatening to test-fire a ballistic missile.

There have been no flights of U.S. reconnaissance planes since March 2, when four North Korean jet fighters flew near an Air Force RC-135S carrying a crew of 17. One of the North Korean jets came within 50 feet of the plane, according to the Pentagon. U.S. officials have since been engaged in what sources described as an intense debate over how to respond to the incident.

Although some officials said no surveillance flights had been scheduled in the 10 days since March 2, other sources said U.S. officials had wanted more frequent flights to monitor any North Korean moves to test-launch missiles but had held back during the deliberations.

The decision not to send escort fighters is another sign that the Bush administration is eager to avoid confrontation with North Korea while it concentrates on Iraq. Another U.S. source confirmed that the decision on the spy planes had been a "restrained" response to the March 2 intercept, which Davis, the Pentagon spokesman, called a "reckless and provocative action" fraught with danger.

Before the incident, North Korea had strenuously protested U.S. reconnaissance flights, alleging that the planes intruded on North Korean airspace. The Pentagon has said the intercepted aircraft was 150 miles from North Korean shores, well within international airspace.

U.S. military aircraft have routinely monitored North Korea for decades, but flights with special surveillance equipment were stepped up as tensions grew over North Korea's nuclear program.

Immediately after the incident, U.S. officials strongly asserted that American forces would exercise "the right" to conduct surveillance. In fact, however, the flights were grounded while the Pentagon and Bush administration officials wrangled over what to do.

Some argued for a strong show of force by sending the spy planes aloft accompanied by fighter jets, according to sources. The advanced U.S. fighter planes "could shoot the MiGs down, no question," said one analyst familiar with the debate.

But others argued that such an incident could start a war. A military official noted the United States has long been "very, very hesitant" to arm and escort reconnaissance flights, on the theory that armaments undermine the argument that the flights are innocent and non-provocative.

Arguments for a more cautious approach eventually prevailed.

"It is pretty restrained for a red-meat Defense Department," said one analyst in Seoul.

The Pentagon has taken care that the spy plane pilots will not be surprised, as they were on March 2,

if MiGs do appear. Advanced detection systems will be trained on the area to detect the approach of any North Korean aircraft.

"You can do that with Aegis, you can do that with AWACS, you can do that with a U-2," said a military source, describing three of the long-range reconnaissance systems available to the military.

Monitoring could be done by ships accompanying the USS Carl Vinson, an aircraft carrier due to arrive in South Korean waters this week to replace the Kitty Hawk, which has gone to the Persian Gulf. The carrier's battle group includes destroyers with Aegis radar.

If North Korean planes were found to be approaching, it is unclear what the U.S. reaction would be. Military sources said the least confrontational course would be to order the spy plane to leave the area. "You could just fly east," away from North Korea, said the senior military officer. Another source, who is not in the military, said the Pentagon was considering keeping fighter planes in the air but at a "remote" distance, from which they could be called in if necessary.

"One thing is sure: You wouldn't be giving a pilot the authority to fire away at will," this source said.

Pentagon officials have said they believe a MiG pilot in the March 2 incident motioned for the reconnaissance aircraft to follow him and land in North Korea. It was "a deliberate attempt to force our aircraft down," Davis said. The RC-135S pilot ignored the gesture.

North Korea captured an American spy ship, the USS Pueblo, in 1968 in what apparently were North Korean waters. One crewman was killed and 82 others were held for 11 months. In 1969 North Korea shot down a U.S. EC-121 reconnaissance aircraft, killing 31 Americans in what has been called the worst single loss of U.S. servicemen in the Cold War.

Staff writers Vernon Loeb and Bradley Graham in Washington contributed to this report.

A North Korean soldier keeps watch along the Demilitarized Zone between North and South Korea. Tensions between the U.S. and the North have escalated over the interception of a U.S. spy plane by North Korean MiGs.