"We appreciate the challenging times in which the people of Japan live with increasing provocations from across the Sea of Japan", Pence said.
"It is a matter of paramount importance for us to seek diplomatic efforts as well as peaceable settlements of the issue", he said.
Vice foreign minister Han told the Associated Press last week that North Korea was prepared to handle a war with the U.S.
The United States is aware of a higher-than-usual level of activity by Chinese bomber planes, signaling a possible heightened state of readiness, USA officials told Reuters on Thursday, but downplayed concerns and left open a range of possible reasons.
Trump, however, in the interview Monday, said "we're doing really well" and that "China has been helping and other people have been helping".
"North Korea is a problem". It has said it has developed a missile that can strike the mainland United States, but officials and experts believe it is some time away from mastering the necessary technology, including miniaturising a nuclear warhead.
"Just in the past two weeks, the world witnessed the strength and resolve of our new president in actions taken in Syria and Afghanistan", he said speaking alongside South Korea's acting President Hwang Kyo-ahn. Even the Korea-U.S. trade agreement could come under scrutiny for "tweaks", the adviser said.
If criticism can be levied at Washington, it is that successive American administrations neglected the threat by either concentrating on nuclear challenges from the Middle East, or by concocting grand concepts which merely hid lack of any action. "While all our options are on the table, President Trump is determined to work closely with Japan, with South Korea, with all our allies in the region, and with China", he said.
And when asked what he plans next, President Trump said, "Wait and see". They also say greater Chinese cooperation is vital.
North Korea says 'don't mess with us' as US plans next move
Trump has warned that if China - North Korea's closest ally - can't help rein in the regime, the US and its allies will. Among the increasing threats are Iran's growing missile capabilities, as well as Iranian subversion in Iraq and Yemen.
The comments dash the hopes of Japanese policymakers, who have said they want to avoid use of the economic dialogue as a forum to discuss a bilateral FTA that may put them under United States pressure to open up highly-protected areas like agriculture.
Asked whether another North Korean nuclear test is imminent, she said, "Some kind of a major provocation like that would draw a pretty significant global response".
"I don't want to telegraph what I'm doing or what I'm thinking", he said.
Pence's economic discussions in Tokyo will be closely watched to see how hard a line Washington is prepared to take on trade.
During the USA presidential campaign, Trump harshly attacked Beijing as a currency manipulator and threatened to slap 45 per cent tariffs on Chinese imports.
He signaled he was out of patience with China on North Korea, saying in a Financial Times interview published April 2 that the US could act on its own to resolve the crisis over North Korea's nuclear program. Many coal ships have been sent back, fuel has been sent back.
Foreign aid projects in North Korea include English lessons and workshops, as well as equipment and training for physiotherapy units.
Another official, speaking on condition of anonymity to discuss an intelligence matter, said the missile was a Scud variant that the USA calls a KN-17.