WASHINGTON — North Korea announced on Wednesday that it would suspend its nuclear weapons tests and uranium enrichment and allow international inspectors to monitor activities at its main nuclear complex. The surprise announcement raised the possibility of ending a diplomatic impasse that has allowed the country’s nuclear program to continue for years without international oversight.

The Obama administration called the steps “important, if limited.” But the announcement seemed to signal that North Korea’s new leader, Kim Jong-un, is at least willing to consider a return to negotiations and to engage with the United States, which pledged in exchange to ship tons of food aid to the isolated, impoverished nation.

A freeze on nuclear activity, if it holds, could significantly ease anxieties over North Korea’s behavior at a time when the Obama administration, in an election year, is focused on halting Iran’s nuclear program and reducing the possibility that Israel could attack Iran. The last significant effort to negotiate a dismantling of North Korea’s nuclear weapons collapsed in the waning weeks of George W. Bush’s presidency more than three years ago.

The United States and other nations have been watching closely to see whether Mr. Kim’s rise to power late last year after the death of his father, Kim Jong-il, would result in a change in North Korean behavior. The signals have been mixed. Only days ago, Mr. Kim delivered a bellicose speech suggesting that he could resort to military actions against South Korea as he consolidated his power.

North Korea also agreed to a moratorium on test launchings of long-range missiles, which have in the past inflamed tensions in the region. But joint statements by the State Department and North Korea’s official news agency gave no indication of when substantive negotiations over the country’s nuclear program — involving the United States and North Korea, along with Russia, China, Japan and South Korea — might begin again.

Kim Jong-un met with soldiers from the Korean People’s Army in southwestern North Korea in February.

North Korea must first arrange with the International Atomic Energy Agency to send its nuclear inspectors, a process that officials said could raise new obstacles and take some time. And senior administration officials cautioned that North Korea still had to show its sincerity before broader discussions could resume. “We’ve made clear that we’re not interested in talks just for the sake and the form of talks,” a State Department official said.

North Korea has agreed in the past to halt its nuclear efforts, only to back out and then return to the table before breaking off talks once more with a flurry of accusations against the United States. The North Korean statement appeared to leave wiggle room for doing so again, saying the country would carry out the agreement only “as long as talks proceed fruitfully.”

“The United States, I will be quick to add, still has profound concerns,” Secretary of State Hillary Rodham Clinton said when she announced the agreement at a House Appropriations Committee hearing on Wednesday. “But on the occasion of Kim Jong-il’s death, I said that it is our hope that the new leadership will choose to guide their nation onto the path of peace by living up to its obligations. Today’s announcement represents a modest first step in the right direction.”

Officials and analysts offered different theories about why Mr. Kim’s government’s would agree now to allow inspectors to return, but most said it could prove to be a significant concession. After years of negotiations, North Korea expelled inspectors and went on to test nuclear devices in 2006 and 2009. American intelligence officials believe that the country has enough fuel for six to eight weapons, but the progress of its newly disclosed uranium-enrichment program at the Yongbyon nuclear complex, conducted without international scrutiny, remains unclear.

Victor Cha, a senior analyst with the Center for Strategic and International Studies in Washington, said that the agreement announced Wednesday differed little from previous ones that had failed to produce breakthroughs, but that it was nonetheless significant because the return of inspectors could shed light on the country’s nuclear progress.

“We haven’t had any eyes on this program for over five years now,” Mr. Cha said in a telephone interview from South Korea’s capital, Seoul. Some analysts and officials said the agreement might signal that the young and inexperienced Mr. Kim had consolidated power and had the backing of his country’s military.

Although administration officials said it was too soon to draw conclusions about Mr. Kim’s intentions, they said there was no doubt that he had directly authorized his negotiators to reach the deal, which the United States first offered in talks last July. An agreement appeared close during a second round of talks, but then the elder Mr. Kim died.

Two days of talks in Beijing last week between American and North Korean negotiators, as well as the Chinese, initially appeared to have produced few concrete results. But after the North Koreans returned home, the country’s leaders unexpectedly and rapidly responded. “This was very much in motion before the leadership transition,” said Daryl G. Kimball, executive director of the Arms Control Association in Washington, who called the agreement a welcome step.

Other analysts said the agreement allowed Mr. Kim to demonstrate his command and to use his early months in power to improve people’s lives after years of food shortages and a devastating famine. “It helps him show to his people that he is a leader who can deal with the Americans and bring back some practical benefits, namely the food aid,” said Kim Yong-hyun, an analyst at Dongguk University in Seoul.

As part of the agreement, the United States said it would send 240,000 metric tons (about 265,000 tons) of food, though it limited the aid to nutritional supplements, rather than the rice and grains that, as two administration officials said, has in previous instances been diverted by the government or the military, or even sold abroad.

The aid is expected to be delivered in monthly shipments of 20,000 metric tons over the next year. The United States also insisted on rigorous monitoring to ensure that the aid would be provided to the neediest, especially women and children, many of whom show the stunting effects of chronic malnutrition. In its statement, the State Department said that in exchange, the United States was “prepared to take steps to improve our bilateral relationship in the spirit of mutual respect for sovereignty and equality” and to allow cultural, educational and sports exchanges with North Korea.

The State Department official cautioned that the agreements “merely unlock the door” to a resumption of negotiations over North Korea’s nuclear program. “We can’t allow the same patterns of the past to repeat themselves,” the official added. “We can’t allow wasting arguments on topics that are irrelevant to the main challenges we face. And that’s simply going to take a long time to work out.”