Chinese President Xi Jinping and Russian President Vladimir Putin, who met on the sidelines of a BRICS summit in China, agree to "appropriately deal" with the North Korean nuclear test, the Xinhua news agency reported.
Trump has also spoken twice this week with Japanese Prime Minister Shinzo Abe.
North Korea has been working to develop a nuclear-tipped missile capable of hitting the United States and has recently threatened to land missiles near the U.S. Pacific territory of Guam.
The leaders of the United States and South Korea on Friday reaffirmed the need to bring Pyongyang back to the negotiating table by applying maximum sanctions and pressure, according to the office of President Moon Jae-in.
The bomb was created to be mounted on its newly developed intercontinental ballistic missile (ICBM), the North said.
The possibility of abandoning the agreement has alarmed economists and some members of the president's own party who fear that such a move would force South Korea to block American manufacturers and farmers from a lucrative market.
Harris and Song talked about the grave threat posed by North Korea's ballistic missile and nuclear weapons programs, as well as bilateral coordination measures to effectively respond to provocations on the Korean Peninsula, she said.
"We once again call on North Korea to come forward to the path of establishing peace solidly on the Korean Peninsula and denuclearization", the statement said.
However, Trump said after the latest missile test that negotiations with Pyongyang were "not the answer".
Moon is also pursuing a diplomatic route to contain the threat from North Korea. Experts believe the move may strike tensions between the two countries. Seoul's National Intelligence Service denied the claim.
The US now has around 28,500 soldiers stationed in South Korea, and Washington also guarantees the country's protection under its nuclear umbrella.
A U.S. official who studies North Korea's military and politics said it was too early to determine if a test supported the North's claim that it has succeeded in developing a thermonuclear weapon, "much less one that could be mounted on an ICBM and re-enter Earth's atmosphere without burning up".
Earthquakes triggered by North Korean nuclear tests have gradually increased in magnitude since Pyongyang's first test in 2006, indicating the isolated country is steadily increasing the destructive power of its nuclear technology. Kim Hyun-bin, Arirang News.
North Korea defends its weapons programs as necessary to counter perceived USA aggression, such as recent air maneuvers with South Korean and Japanese jets.
"He reaffirmed the ironclad US commitment to the Mutual Defense Treaty, which states that a North Korean attack on one is an attack on both nations", she said.