Two U.S. B-1 bombers flew over South Korea on Tuesday, September 13 in a show of force and solidarity with its ally after North Korea's nuclear test last week, while a U.S. envoy called for a swift and strong response to Pyongyang from the United Nations, Reuters reports.

Speaking in the South Korean capital on Tuesday, Sung Kim, the U.S. envoy on North Korea, added that the United States remained open to authentic, meaningful dialogue with Pyongyang on ending its pursuit of nuclear weapons.

"Our intention is to secure the strongest possible (U.N. Security Council) resolution that includes new sanctions as quickly as possible," Kim told a news briefing after meeting his South Korean counterpart.

He said the United States would work with China, North Korea's major diplomatic ally, to close loopholes in existing resolutions, which were tightened with Beijing's backing in March.

"China has been very clear that they understand the need for a new U.N. security council resolution in response to the latest North Korean nuclear test," Kim said.

However, China and Russia, which strongly oppose a recent decision by the United States and South Korea to deploy an advanced anti-missile system in the South to counter the North's missile threat, have shown reluctance to back further sanctions.

"Both sides think that North Korea's nuclear test is not beneficial to peace and stability on the Korean peninsula," China's official People's Daily newspaper said on Tuesday following a high-level China-Russia security meeting in Beijing.

"At present, we must work hard to prevent the situation on the peninsula continuing to escalate, and put the issue of the nuclearization of the peninsula back on the track of dialogue and consultation," it said.