The United States is pushing for tough sanctions against the Democratic People's Republic of Korea and warned Pyongyang on Wednesday against any "provocative" act, media reported.
"We anticipate formal steps in the Security Council in the immediate future," Kurt Campbell, top US diplomat for East Asia, told reporters in Seoul, according to Reuters.
He added that Washington was "in the middle of really rather intense deliberations" at the United Nations.
Security Council resolutions have already banned the DPRK from developing nuclear and missile technology.
In December, Pyongyang launched a long-range rocket. The West suspected it was a disguised missile test, but Pyongyang said the launch was intended only for scientific and peaceful purposes.
Recent reports said the DPRK is possibly preparing for a third nuclear test.
"We are very clear in our position that provocative steps are to be discouraged," Campbell told reporters when asked about the nuclear test speculation, AFP reported.
He also stressed that Washington was in "very detailed conversations" with key players such as China and Russia.
China has been insisting on denuclearization of the Korean Peninsula and reconciliation between the DPRK and the Republic of Korea.
Now is actually a good time to improve the situation on the Korean Peninsula, and the countries involved should deal with it cautiously, said Liu Jiangyong, deputy dean of the Institute of Modern International Relations at Tsinghua University.
ROK President-elect Park Geun-hye has taken a more flexible stance toward the DPRK, compared with her predecessor Lee Myung-bak, and this has paved the way for economic cooperation between Seoul and Pyongyang, Liu said.
DPRK leader Kim Jong-un did not criticize Park's victory, which, Liu said, has helped to create a friendly atmosphere.
"As long as Pyongyang refrains from moves that are provocative, I am optimistic about the situation on the peninsula," Liu said.
Zhang Liangui, an expert on Korean studies at the central Party school, said the news about a third nuclear test was possibly leaked intentionally by the DPRK to see what the response would be.
"If the international community responds furiously, Pyongyang may put off the plan," Zhang said.
A flurry of diplomatic activity has been under way because tension remains high in the region.
The ROK will send a delegation of special envoys to China next week to meet Xi Jinping, China's top political leader and head of the military, and other government officials, Seoul-based Yonhap News Agency reported.
After meeting Park later on Wednesday, Campbell was scheduled to continue his trip to Japan, another key player in the Six-Party Talks on the denuclearization of the Korean Peninsula, which has been involved in disputes with the ROK and China over territorial and historical issues.
Washington hopes the ROK and Japan can put a lid on their disagreements and seeks to reassure Tokyo in its standoff with China, analysts said.
Pu Zhendong contributed to this story.