Prime Minister Shinzo Abe and his visiting British counterpart, Theresa May, vowed Thursday in Tokyo to jointly deal with the North Korean military threat and step up efforts to avoid economic confusion that could be caused by Britain’s decision to leave the European Union.

May’s visit coincided with rising regional tension with North Korea threatening to take more provocative actions. South Korean intelligence officials reportedly said Pyongyang appears prepared to conduct another nuclear test.

The two leaders also agreed that China should play “a key role” in applying stronger pressure on the North to stop its nuclear weapons and ballistic missile programs, Japanese officials said.

In recent years, Britain has been actively trying to strengthen military cooperation with Japan, including through the exchange of defense technologies.

In a joint statement, Tokyo and London called for strict implementation of U.N. Security Council resolutions against North Korea.

They also pledged to bolster security cooperation in the Indo-Pacific region, emphasizing the importance of rule of law and opposing unilateral moves aimed at changing the status quo.

“The close cooperation between our two countries is particularly important at this critical juncture with North Korean provocation presenting an unprecedented threat to international security,” May told a joint news conference with Abe at the State Guesthouse in Tokyo’s Akasaka district. “I want to begin by expressing the U.K.’s strong sense of solidarity with Japanese people.”

“We condemn North Korea in the strongest terms possible for this reckless act,” she added, referring to the reclusive state’s latest test-firing of a ballistic missile.

Since Tuesday, Abe has worked to demonstrate Japan’s ties with key allies to show strength in the face of Pyongyang’s saber-rattling.

Abe held separate teleconferences with U.S. President Donald Trump, South Korean President Moon Jae-in and Australian Prime Minister Malcolm Turnbull over the past two days, all sending a clear message: Japan and its allies will not tolerate North Korean provocations and China should do more to stop Pyongyang’s ongoing nuclear and ballistic missile development.

May, meanwhile, has another aim during her visit: Easing anxiety among Japanese firms over Britain’s planned exit from the EU.

May was accompanied by International Trade Secretary Liam Fox and a delegation of 15 senior business leaders, including representatives from Barclays, the Scotch Whisky Association and Aston Martin.

During the summit meeting, Abe asked May to minimize Brexit’s impact on Japanese firms by enhancing transparency and predictability, Japanese officials said.

At about 2:10 p.m. Thursday, May visited the Palace Hotel Tokyo to attend a Japan-Britain business forum. Among those in attendance were Abe, Fox and business leaders including Hitachi Ltd. Chairman Hiroaki Nakanishi.

“For Japanese companies, Britain is an important base of manufacturing, sales, research and development and more in Europe,” Abe told the audience at the outset of the forum.

Abe said Japanese firms have about 1,000 offices and factories in Britain, providing more than 160,000 jobs. Abe noted that three Japanese firms account for 50 percent of the roughly 1.7 million cars assembled in Britain each year.

“Preparing for an exit from the European Union, Britain now faces major changes. For Britain, Europe, the international society and the world economy, it is very important that the U.K.’s exit from the EU goes smoothly and successfully,” Abe said.

In response, May pledged to maintain her commitment to smooth, free trade relations with Japan.

Later in the day, May attended a special session of the National Security Council at the Prime Minister’s Office in Tokyo concerning the North Korean threat. It is extremely rare for a foreign leader to attend such a session, where discussions are kept tightly secret. The only other foreign leader to attended was Australia’s then-Prime Minister Tony Abbott during a 2014 visit.

At the outset of the session, May said she is willing to cooperate with Japan to jointly deal with North Korea.

May, who arrived in Japan on Wednesday on a three-day trip, also inspected the helicopter destroyer Izumo at the Maritime Self-Defense Force’s Yokosuka base, accompanied by Defense Minister Itsunori Onodera. The 19,500-ton, 248-meter-long Izumo is officially called a “destroyer” but is in fact a massive helicopter carrier with a flat, 248-meter flight deck.

On Friday, May plans to leave Japan after paying a courtesy visit to Emperor Akihito at the Imperial Palace in Tokyo.