CAMP DAVID, Md. - President Bush and South Korean President Lee Myung-bak said Saturday that there still is a chance to make progress on eliminating North Korea’s nuclear weapons programs, urging critics to see what Pyongyang says in a required declaration before deciding whether nations are being too lenient.

“We need persistent patience, ladies and gentlemen,” Lee said, side-by-side with Bush here at the presidential retreat where the two leaders met for two days of talks. “It’s difficult to convince North Korea to give up its nuclear weapons programs, but it is not impossible.”

Nuclear talks between North Korea and five other nations, including the United States and South Korea, are stalled over whether Pyongyang will hand over a promised full declaration of its nuclear programs — its uranium enrichment program as well as alleged proliferation activities — in return for concessions. The North made unprecedented progress last year, including closing its working plutonium reactor, but work slowed in a dispute over how much the North had to reveal in the declaration, due in December.

The Bush administration apparently has decided that the declaration’s exact contents are less important than an assurance that the nuclear negotiators can check up on Kim Jong Il’s government to make sure it has told the truth. The administration is arguing that although it has scaled back its demands about what the North must admit about its nuclear past, it will still get the information it wants, along with new ways to make sure Pyongyang isn’t cheating.

But Bush critics, especially in the right wing of the Republican Party, claim the president is lowering the bar for the nation he once included in his so-called “axis of evil.” They claim Bush appears more interested in striking a deal with Pyongyang before he leaves office than making North Korea honor its pledge.

“Why don’t we just wait and see what they say before people go out there and start giving their opinions about whether or not this is a good deal or a bad deal?” Bush said.

In his comments defending his administration’s approach, the president stressed the importance of establishing effective ways to verify whatever North Korea says.

“The burden of proof is theirs,” he said. “We and our partners will take a look at North Korea’s full declaration to determine whether or not, you know, the activities they promised they could do can be verified and then we’ll make a judgment of our own.”

He added: “Obviously, I’m not going to accept a deal that doesn’t advance the interests of the region.”

Lee, a pro-American conservative, has taken a stronger stance against North Korea’s nuclear program than his more liberal predecessor, Roh Moo-hyun. Lee’s get-tough rhetoric against his communist neighbor may even be tougher than Bush’s at the moment.

But he and Bush appeared mostly on the same page during their joint appearance.

“I think it is unconstructive to have too many doubts before the process begins,” said Lee, speaking through a translator.

Bush said “of course they may be trying to stall” by not turning in the declaration yet. “It’s hard to tell what’s going on,” he said, because North Korea is such a closed society, ruled by a dictatorship regime.

But, he said, “The key thing is we haven’t abandoned the efforts to solve this peacefully and diplomatically.”

Critics would be parsing the wording from Bush and Lee about what North Korea must do to try to divine any movement in positions. Bush said North Korea has to “provide a full declaration of its nuclear programs and proliferation activities in a verifiable way.” Lee said the “declaration should be complete and correct and verification — I’m not sure how long that’s going to take.”

Relations between the United States and South Korea have been tense in recent years and Lee has said that improving them is a top priority for him.

Lee made the United States his first foreign trip. Bush was doing his part too, extending the Camp David invitation to Lee, something reserved for only the closest allies. Bush said no Korean leader had ever been to the rustic, wooded mountaintop compound before. Bush and Lee also announced that the U.S. president would make a reciprocal visit to South Korea sometime this summer.

Bush said the main purpose of the visit was to “strengthen the relationship between our two countries — and I believe we have done so.”

Bush ticked through key issues for Seoul.

He said the leaders agreed to maintain the current U.S. troop levels in South Korea. But in a move the U.S. says is a sign of confidence in the South Korean military, the United States is repositioning U.S. troops on the Korean peninsula into two main hubs south of Seoul and is working on a transition of wartime operational control to the South Koreans.

Bush also said he was directing administration officials to work with Congress to grant Seoul’s request to have the same access to technical information as NATO and other allies. “I strongly support this,” he said.

The two sides also took a big step forward this week toward South Korea’s goal of its citizens being exempted from needing a visa to travel to the United States.

And Bush pledged to “press hard with the United States Congress” for approval of a pending free-trade agreement with South Korea. If ratified, the free-trade deal would be the largest since the North American Free Trade Agreement, adding an estimated $20 billion or more a year to two-way trade between the two nations, according to the Bush administration.

On Friday, South Korea announced it would lift its ban on U.S. beef imports, removing one obstacle to getting lawmakers to ratify the trade deal.

South Korea was the third-largest foreign market for U.S. beef before it banned imports in December 2003 over the possibility of mad cow disease. Even with the beef spat resolved, however, the trade deal still faces concerns by Democrats and automakers and a narrowing legislative calendar that could push the issue into the next administration.

The South Korean Agriculture Ministry said it will allow U.S. beef imports from cattle younger than 30 months. Younger cows are believed to be less at risk for mad cow disease. South Korea said it would allow beef from older cattle after the U.S. strengthens controls on feed to reduce chances of infection. Sen. Max Baucus, D-Mont., chairman the Senate Finance Committee, said he will block consideration of the trade agreement until all cuts of U.S. beef from cattle of all ages are on Korean store shelves.

Beef was on the menu for the Camp David dinner Friday night between Bush and his wife, Laura, and the South Korean leader and his wife, Kim Yoon-ok. Lunch on Saturday, coming after their joint news conference and capping the get-acquainted session, was fried chicken and potato salad.