Second Vice Foreign Minister Cho Hyun reminded a forum here that Washington has repeatedly put "all options" on the table over North Korea's nuclear and ballistic missile programs.
Japanese Prime Minister Shinzo Abe and South Korean President Moon Jae In held talks Thursday in the Russian Far East, where they are set to confirm coordination in seeking tougher sanctions on North Korea in the wake of a recent nuclear test.
Moon and Putin met on the sidelines of the economic summit Wednesday, where the South Korean leader tried to persuade his Russian counterpart to agree to banning oil exports to North Korea.
"Pyongyang's missile and nuclear programme is a crude violation of UN Security Council resolutions, undermines the non-proliferation regime and creates a threat to the security of northeastern Asia", Putin said at a joint news conference. "We've already raised it during the telephone talks on September 3 and today we followed with the detailed discussions", Putin said. "But we should be careful that this does not translate into an escalation of war or cause miscalculation of North Korea".
Washington, Seoul and Tokyo have been pushing for stronger sanctions to punish Pyongyang over its nuclear activities, such as denying the country oil supplies.
But he warned the North could fire ballistic missiles at any time from easily concealed mobile launchers.
US Ambassador to the United Nations Nikki Haley accused North Korean leader Kim Jong Un on Monday of "begging for war" with a series of nuclear bomb and missile tests.
"The time for half-measures in the Security Council is over".
North Korea, meanwhile, has not ceased its daily threats to attack the United States and South Korea. Kang told parliament that her nation is working with the US for the "strongest" measures against North Korea.
Russian President Vladimir Putin says further sanctions and threats against Pyongyang are"useless
H-bombs, more formally called thermonuclear devices, date to the 1950s and have the potential to be far stronger than simpler fission bombs like those used on Hiroshima and Nagasaki by the United States at the end of World War II.
U.S. Defense Secretary James Mattis says that South Korea will not face North Korean provocations alone, amid speculations that North Korea could test another long-range missile on the anniversary of its founding day on Saturday.
The allies have boosted defense measures in response to Pyongyang's provocations, including by completing the deployment of a USA missile defense system in Seongju, South Korea, earlier in the day. "We must act with calm and avoid steps that could raise tensions". "China expresses serious concern over the relevant movements", Geng said.
But sending USA nuclear weapons back to South Korea would be a more drastic step, contradicting the efforts of multiple administrations to "denuclearize" the Korean Peninsula.
It remains unclear whether North Korea tested, as it claims, a hydrogen bomb ready to be mounted on an ICBM.
Japan's Defense Minister said Wednesday the explosive device detonated deep under a North Korean mountain Sunday had a yield of up to 160 kilotons.
The official cast doubt on attempts to prevent North Korea from obtaining a nuclear weapon using methods employed in the past, suggesting the country's intentions are unlike those of other nations with nuclear ambitions.
"Following the operation, one B-1B flew to Misawa Air Base to be a static display for the Misawa Air Festival, while the other B-1B returned to Andersen Air Force Base", she added.