VANCOUVER, British Columbia — Secretary of State Rex Tillerson called on Tuesday for nations to step up the U.S.-led “maximum pressure” campaign against North Korea by thwarting efforts to evade sanctions and interdicting ships conducting illicit trade with the pariah nation.

The uncompromising message, delivered to a gathering of 20 nations that were on America’s side during the Korean War, was coupled with skepticism among the allies over North Korea’s sincerity in its recent diplomatic opening with the U.S.-allied South.

“We must increase the costs of the regime’s behavior to the point that North Korea must come to the table for credible negotiations,” Tillerson said in his opening remarks at the meeting on Canada’s western coast. The meeting convened days after a mistaken missile alert caused panic on Hawaii, a stark reminder of the fears of conflict with the North.

“We will not allow North Korea to drive a wedge through our resolve or solidarity,” Tillerson said.

South Korean Foreign Minister Kang Kyung-wha said its talks with North Korea, leading to its participation in next month’s Olympics being hosted by the South, are a “significant first step toward restoring inter-Korean relations.”

But she conceded that North Korea has yet to show any intention to fulfill its obligations on denuclearization of the Korean Peninsula.

Japanese Foreign Minister Taro Kono was blunter. He said the North “wants to buy some time to continue their nuclear and missile programs.”

British Foreign Secretary Boris Johnson told reporters that in spite of the inter-Korean talks, “the North Korean regime is still going down the path of the acquisition of an ICBM (intercontinental ballistic missile) tipped with a nuclear device that could have incalculable geostrategic consequences.”

The meeting was attended by foreign ministers and senior diplomats of nations that sent troops or humanitarian aid to the U.N. Command that supported South Korea in the fight against the communist North and its allies during the 1950-53 Korean War. It’s a diverse gathering of mostly European and Asian nations, as well as Australia, New Zealand and Colombia.

The delegates were briefed Monday night by Defense Secretary Jim Mattis. A senior State Department official described that as a chance to demonstrate that U.S. has an integrated strategy and to raise confidence that it definitely prefers a diplomatic solution over resorting to military action.