North Korea tested new engines for intermediate-range ballistic missiles, its state media said, a move that could help Pyongyang deliver quick strikes on US bases in places such as Guam.

Tests were conducted on Nov. 11 and 14 on “new-type high-thrust solid-fuel engines” for “further enhancing the strategic offensive capabilities” of North Korea’s armed forces, the official Korean Central News Agency reported Wednesday.

The tests were for a first and second stage of a missile, and North Korea released images on the event on its state media. In the past, Kim Jong Un’s regime has conducted tests of missiles a few months after engine tests.

North Korean state media frequently says that its arsenal of ballistic missiles is capable of delivering nuclear weapons.

The announcement of the missile tests comes as the US is hosting the Asia-Pacific Economic Cooperation summit in San Francisco. Isolated North Korea is not a member, but the tests shine a light on Kim’s nuclear program ahead of high-stakes talks on the summit’s sidelines between President Joe Biden and Chinese leader Xi Jinping.

Secretary of State Antony Blinken met his counterparts from Japan and South Korea on the sidelines of APEC to discuss North Korea’s “increasingly destabilizing actions,” the State Department said in a statement on Tuesday. Blinken also reaffirmed the US’s “ironclad commitment” to defend Japan and South Korea, which host the bulk of the America’s military personnel in the region.

While the US removed its deployments of nuclear weapons from Japan and South Korea decades ago, it maintains what the Pentagon bills as America’s largest munitions depot in the world in Guam. The jungle-strewn island is home to a US Air Force base with bombers capable of delivering nuclear strikes in places such as North Korea and further afield.

North Korea has been modernizing its ballistic missile arsenal over the past few years by testing and deploying solid-fuel rockets that are easier to hide, quick to deploy and capable of being sent into flight before the US and its allies in the region could launch a counterstrike to shoot the missiles on the pad.

Pyongyang had already fired 28 ballistic missiles and two space rockets so far this year. They included four intercontinental ballistic missiles that could hit the US mainland. Kim’s regime launched more than 70 ballistic missiles last year, a record for the state.

In July, North Korea tested its new solid-fuel Hwasong 18 ICBM, which flew longer than any of its other ICBMs and appeared designed to carry a multiple nuclear weapons payload. This increases the chances that at least one bomb could slip past interceptors and make its way to a target.

Liquid-fuel ballistic missiles, which were used almost exclusively by North Kore before Kim Jong Un took power, generally take more time to prepare as propellant is added to their tanks. This makes them vulnerable to attack before taking off.