As North Korea carries out a precarious power transfer, South Korean policymakers face a growing challenge to influence a neighbor that has rejected decades of their appeals, compromises and policies.

So far, the ascension of North Korean heir apparent Kim Jong Eun shows no outward signs of turmoil, with Pyongyang’s state-run news agency cranking out testimonials of loyalty from soldiers and Workers’ Party members. But in Seoul, at least for some, the post-Kim Jong Il transition resembles a nerve-rattling spectator event — viewed from afar, with no say in the outcome.

“We are powerless to influence North Korea’s behavior,” said Hahm Chaibong, president of the Asan Institute for Policy Studies in Seoul. “We have tried everything at this point.”

The feeling of helplessness here reflects Seoul’s utter inability to solve the North Korean policy puzzle — among the toughest in the world, diplomats say. When South Korea offers aid or other incentives, North Korea uses them only to enrich its regime. When South Korea takes a hard-line approach, as President Lee Myung-bak has done, North Korea turns all the more antagonistic, nuzzling closer to China in the process.

Since the announcement of Kim Jong Il’s death on Monday, China has reinforced its role as the lone country with close ties to Pyongyang. The China-North Korea relationship is complex, experts say, and Chinese leaders push frequently — with little success — for economic reforms in North Korea. But China also has a clear, broader goal: It wants to prevent North Korea’s collapse, unwilling to risk a unified, democratic peninsula with U.S. troops potentially stationed on its border. As such, senior Chinese officials have spent the week giving public statements of support for Kim Jong Eun.

Thursday, Lee offered his own comments about North Korea as it breaks in its third leader in six decades, telling lawmakers that the “early stabilization’’ of Pyongyang “is in the interests of neighboring countries,” the Yonhap news agency said.

Even in normal times North Korea has little use for South Korea’s advice. But the country is likely to turn further inward, analysts say, as Kim Jong Eun, thought to be in his late 20s, tries to build his power base. The new leader dubbed the “Great Successor” lacks the clout to make major reforms — especially those that would satisfy other countries in the region, which have long tried to push for North Korea’s denuclearization.

Efforts to reach the North

South Korea has tried almost everything. For 10 years before Lee took power, a succession of liberal leaders treated North Korea as a needy but troubled brother. Seoul offered aid, launched joint investment projects and held summit meetings with Kim Jong Il. But the so-called “Sunshine Policy” backfired: North Korea built its nuclear weapons stockpile but not its economy.

Lee, who took office four years ago, has taken an opposite approach, cutting back on the aid of his predecessors and instead offering North Korea a giant proposal: He’d help them build up their country if they relinquished their weapons. But North Korea rejected the idea almost immediately, likely seeing the weapons as its greatest form of leverage, experts say.

“I think the South Koreans hope to see North Korea evolve gradually toward a market economy with a more reasonable political leadership in the same way that China and Vietnam have,” said Gregg Brazinsky, an East Asia specialist at George Washington University. “The key question is, how do you bring this about?”

South Korea’s approach toward its neighbor is complicated by a growing group of defectors who advocate for regime collapse — something the government itself has never pushed for. Wednesday, representatives of some 30 defector groups met near the Demilitarized Zone that divides the peninsula for an event they hoped would spark protests in a country with rigid social controls.

Seoul’s National Intelligence Service urged them not to hold the event, fearful of antagonizing the North. The defectors held it anyway.

The defectors first printed fliers that documented Kim Jong Il’s lavish lifestyle and described North Korea as a “fenceless prison.” They then stuffed the fliers into five massive balloons. They activated a timer and let the balloons fly, hoping for good winds that might send the balloons well north of the DMZ — perhaps into North Hwanghae province.

The rally was partly a made-for-television event, media members outnumbering defectors. But some of the activists knew from their own experiences the power of what they were sending. They, too, had once found information that challenged North Korean propaganda. And they wondered about life in China or South Korea.

Among South Korea’s 20,000 defectors, some have stories about watching bootlegged American movies (like “Rambo” and “Home Alone”) or South Korean soap operas. Some recall finding photos of beautiful women, with perforations around their bodies. The message: “Cut and use. Come to ROK for freedom.”

Kim Sung-min, a defector who now runs a radio station, said he hoped the Wednesday event would erode North Koreans’ trust in their own government — even if only a little.

“North Koreans still don’t have strong emotions against the regime,” said another defector, Jang Se-yul, who fled the country in 2008. “They have complaints, sure, but there is also hope. What we want to do through sending the leaflets is tell them that their hope is misplaced. We want to get them ready to make their own choices.”

Yoonjung Seo contributed to this report.