SEOUL, South Korea -- President Obama's envoy began a rare trip to North Korea Tuesday for the highest-level talks with the communist country in more than a year. A senior U.S. official warned of strong sanctions against Pyongyang unless it rejoins international nuclear talks.

Envoy Stephen Bosworth's mission is to find out whether North Korea will return to the stalled international talks on ending its nuclear programs after carrying out an atomic test blast in May and quitting the six-nation negotiations.

Bosworth's delegation flew to Pyongyang from a U.S. military base near Seoul, the U.S. Embassy in Seoul said. North Korea's official Korean Central News Agency later said in a one-sentence dispatch that the delegation arrived in Pyongyang.

Footage from broadcaster APTN in Pyongyang showed Bosworth and Washington's lead nuclear negotiator, Sung Kim, arriving at an airport in Pyongyang, shaking hands with North Korean officials and posing for photos.

In Washington, a senior U.S. official said Bosworth had no new incentives for the North.

"We don't intend to reward North Korea simply for going back to doing something that it had previously committed to do," the official told reporters, speaking on condition of anonymity during the background briefing. "There are no inducements or incentives other than the fact that should they resume the talks, then they would be in a position to pursue some of the things that were possible should they proceed with denuclearization."

The official noted that there have been suggestions and indications that Pyongyang may be ready to rejoin the talks involving China, Japan, the two Koreas, the U.S. and Russia. But he added, "You never know what the answer is until you ask and get the question answered."

The official warned that the North faces strong U.N. sanctions if it does not agree to return to negotiations.

"At a minimum, I think it will reinforce the intention of the international community to continue a very strong enforcement" of U.N. sanctions resolutions adopted to punish the North for its nuclear test and other provocations, the official said.

U.S. Secretary of State Hillary Clinton told reporters Monday that she hopes Bosworth is successful in persuading the North Koreans to return to the nuclear talks, and that the North will work for "a new set of relationships with us and with our partners."

This week's talks -- the first direct U.S.-North Korean talks since Obama took office in January -- come after a year of threatening rhetoric and rising tensions on the Korean peninsula. Earlier this year, Pyongyang expelled U.N. nuclear inspectors, restarted its atomic facilities, test-fired a long-range rocket and a series of ballistic missiles, quit six-party talks and conducted the nuclear test.

Former nuclear envoy Christopher Hill was the last high-level official to visit for direct talks. He was in North Korea in October 2008.

Pyongyang says it needs nuclear bombs to counter the strong U.S. military presence in South Korea. The impoverished country has also used the atomic threat to win aid and other concessions from regional powers wary of the unpredictable neighbor.

But in recent months, the North has tried to reach out to the U.S. and South Korea in an abrupt about-face that analysts and officials say shows the impoverished regime is feeling the pain of U.N. sanctions. Since August, the North has freed detained U.S. and South Korean citizens and taken other conciliatory steps, including inviting Bosworth for direct talks.

Neither side has said which North Korean officials Bosworth will meet in Pyongyang during his three-day trip, though he is widely expected to sit down with Kang Sok Ju, the first vice foreign minister, who is considered the chief foreign policy strategist for reclusive leader Kim Jong Il.

North Korea has no choice but to rejoin the disarmament process since Washington has made it a condition of bilateral contact, said Koh Yu-hwan of Seoul's Dongguk University.

He said North Korea likely will push for a U.S. commitment on a peace treaty, but State Department spokesman Kelly said the issue of a peace treaty is "not on our agenda" and the issue should be discussed at the six-party talks.

Analyst Paik Hak-soon of the private Sejong Institute think tank said it was too early to expect a major breakthrough.

"It'll be a preparatory step ahead of full-fledged negotiations. They'll disclose their positions and listen to each other, find and understand what their common interests are and what differences they have," he said.

In addition to Sung Kim, Bosworth was accompanied by nuclear and Asia specialists from the Defense Department and the White House. The delegation is to return to Seoul on Thursday before continuing onto Beijing, Tokyo and Moscow to brief other parties in the international talks before returning to Washington.