Pence reiterated that after years of North Korea testing the US and its neighbors in East Asia with its nuclear ambitions, the USA "era of strategic patience is over".
North Korea's deputy in the United Nations on Monday night also refused to confirm whether Pyongyang had ignored China's request to meet, while complaining that nuclear war could break out at any moment.
China and North Korea maintain "normal contacts, including normal business contacts", said Chinese Foreign Ministry spokesman Lu Kang, when asked about the trucks.
With a United States aircraft carrier group steaming to the area in a show of force, fears of a confrontation have been rising.
For now, the president isn't saying how he intends to deal with the North Korea problem.
Vice foreign minister Han told the Associated Press last week that North Korea was prepared to handle a war with the U.S.
Experts say the North may soon carry out its sixth nuclear test.
"But the era of strategic patience is over", he declared.
Since entering office, President Donald Trump, like his predecessor, Barack Obama, has pressed China to use its political and economic leverage over North Korea, its once-close ally.
North Korea has conducted several missile and nuclear tests in defiance of United Nations sanctions and has said it has developed a missile that can strike the U.S. mainland.More news: North Korea celebrates 'Day of the Sun' with defiant show of might
Trump made the comment to a CNN reporter after kicking off the 139th annual Easter egg roll with First Lady Melania Trump.
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. -South Korean military exercises being staged now are the largest-ever "aggressive war drill". He also met with American troops stationed at the joint US-South Korean military camp.
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".
Meanwhile, China made a plea for a return to negotiations.
"Think of it - he's working so nicely that many coal ships have been sent back, fuel is being sent back", Trump said of Xi.
Earlier, after discovering "great chemistry" with Chinese President Xi Jinping over "the most attractive piece of chocolate cake" at Mar-a-Lago, Trump had confided, "I explained. that a trade deal with the USA will be far better for them if they solve the North Korean problem!"
South Korea will begin mass-producing the missiles next year, reports the Yonhap News Agency, citing the Defense Acquisition Program Administration (DAPA), the South Korean arms procurement agency.
It just wouldn't make sense for him to start a trade war with Beijing while it's complying with worldwide sanctions aimed at the curtailment of North Korea's nuclear program, Trump says. -South Korean installation, which is just outside the 2.5-mile wide (4 kilometers) DMZ.
Vice President Mike Pence arrived in Japan to deliver a message to Prime Minister Shinzo Abe. "But dialogue for the sake of having dialogue is meaningless".
Pence's visit came after Pyeongyang's military parade during which the country exhibited what seems to be ballistic missiles. No one should mistake the USA resolve, he said, also noting that Washington was seeking security "through peaceable means, through negotiations".