SEOUL - The United States is open to diplomacy with the Democratic People's Republic of Korea's (DPRK) new leaders but they must improve frosty ties with Seoul and show seriousness about nuclear disarmament, a senior US diplomat said on Wednesday. 

Kurt Campbell, the US assistant secretary of state for East Asia and the Pacific, arrived in Seoul on Tuesday for a two-day visit involving attendance at a forum organized by the Korea Society. 

"We are open to diplomacy with the DPRK, but there is a very clear set of steps that we think are necessary," the diplomat said after meeting with Lim Sung-nam, the Republic of Korea's (ROK) top envoy to stalled talks over ending Pyongyang's nuclear program, and Vice-Foreign Minister Kim Jae-shin. 

"We agreed the path is open to the DPRK toward the resumption of talks and improved relations with the United States and the ROK," Campbell said. "(But) the road to improve these relations runs through Seoul for the DPRK." 

His remarks came as the ROK steps up calls for dialogue with the DPRK, an attempt to mend cross-border ties that reached their lowest ebb in 2010 following two deadly border conflicts. 

The US and its allies Japan and the ROK "are still waiting to see whether the new government in the DPRK is prepared to take the necessary steps", Campbell told reporters. 

Zhang Liangui, an expert on Korean Studies at Party School of Central Committee of Communist Party of China, told China Daily that Campbell's remark on Wednesday shows Washington's "pertinency" in policymaking in response to Pyongyang's recent attitudes toward the peninsula's nuclear issue. 

The DPRK has stressed that its policy remains unchanged after the death of Pyongyang's former leader Kim Jong-il last December, and the takeover by his youngest son Jong-un. 

However, Pyongyang recently vowed never to deal with Seoul's conservative leader Lee Myung-bak, regularly censured by Pyongyang's state media for his hardline policy. 

"Given Pyongyang's recent stances toward denuclearization and its ties with Seoul, it may not give a positive response to the possible accesses proposed by Campbell to either the resumption of Six-Party Talks or the improvement of DPRK-ROK ties," Zhang said. 

Meanwhile, the US special representative for the DPRK policy Glyn Davies is paying a visit to Russia from Tuesday to deepen cooperation and share perspectives on Pyongyang, according to the US Department of State. 

Lim, the envoy with Seoul, is expected to visit Russia next week to meet his Russian counterpart and Deputy Foreign Minister Igor Morgulov, Yonhap News Agency said on Tuesday, adding that the schedule has not been finalized. 

Recent frequent exchanges of views among the related parties in the Six-Party Talks show that the countries concerned "have decided to wrap up hesitation" after the death of Kim Jong-il , Zhang said. 

The nuclear talks grouping the DPRK, the ROK, China, Japan, Russia and the US were last held in December 2008. Pyongyang walked out in April 2009.