Russian foreign minister Sergey Lavrov warned the USA against "unilateral actions like those we saw recently in Syria" and urged the U.S. to "follow the line that president Trump repeatedly voiced during the election campaign".
The official briefed reporters on customary condition of anonymity after U.S. Vice President Mike Pence met Japanese Deputy Prime Minister Taro Aso in Tokyo to launch the U.S. -Japan Economic Dialogue.
Pence said after the meeting that Trump believes it is in America's interest to negotiate economic deals on a bilateral basis.
While business leaders in Seoul have been critical of the South Korean practice of imposing non-tariff related trade barriers, especially in the auto industry that accounts for 80 percent of the USA trade deficit, they are overall supportive of the KORUS FTA.
Pence, his wife Karen and two daughters walked inside the main hall of colorful Senso-ji temple Tuesday as incense burned.
Trump campaigned for office on an "America First" platform, saying he would boost USA manufacturing jobs and shrink the country's trade deficit with countries like Japan. It is his first trip to Asia as vice president.
The Trump administration has said military action remains an option for dealing with North Korea.
The South Korea/U.S. free trade agreement (KORUS FTA) that took effect in 2012 was the largest trade deal implemented during the administration of former President Barack Obama.
In early March, the North simultaneously fired four ballistic missiles off its east coast, three of which fell provocatively close to Japan, in what it said was a drill for an attack on US bases in the country. Pressure on North Korea is crucial, the prime minister said. He described the U.S. -Japan alliance as the "cornerstone" of regional security.
But the meetings could indicate how forcefully the US will pressure Japan to further open its farm and automotive sectors.
The recent surge in tensions on the Korean Peninsula finds Beijing on the outs with both North and South Korea, while many critics have yet to be convinced by its insistence that its influence with Pyongyang has been exaggerated.
"My understanding is that our talks are premised not on friction but on cooperation", Aso told reporters before Pence's arrival. When asked about his next move, he said, "You'll see".
Pence reassured Prime Minister Shinzo Abe on Tuesday that the US considers its alliance with Japan to be a cornerstone of security in the region.
The South Korean official said that while Wu was sometimes "abrasive" during the early rounds of Six Party talks, "he was just the person we needed at the time to keep the talks alive".
In Moscow, Russian Foreign Minister Sergey Lavrov, speaking to reporters Monday evening, said he hopes "there will be no unilateral actions like those we saw recently in Syria and that the USA will follow the line that President Trump repeatedly voiced during the election campaign".
"But at the same time", the prime minister said, "dialogue for the sake of dialogue is valueless and it is necessary for us to exercise pressure North Korea so that it comes forward and engages in this serious dialogue".
Wu has earned a number of friends in South Korea and a reputation as a "credible" diplomat over the years, according to one Asian diplomat who declined to be named because he was not authorised to speak to the media.
Tokyo is the second stop on Pence's 10-day tour of Asia, a trip aimed at emphasizing that U.S. President Donald Trump wants to boost U.S. trade in the region even though he killed the 10-nation Trans-Pacific Partnership (TPP) trade pact shortly after taking office. Japan wants to avoid opening talks on a bilateral trade deal for fear of being pressured into opening up highly protected areas of its economy, such as agriculture.
Pence said on Monday the world had seen Trump's resolve in the past two weeks, with a USA missile attack on a Syrian airfield and the dropping of a powerful non-nuclear bomb on Islamic State fighters in Afghanistan.
Pence told business leaders before leaving Seoul that the Trump administration is reviewing all trade agreements as part of its "America First" policy.