South Korea and Japan are considering having F-35B stealth aircraft launch from the deck of amphibious assault ships, according to reports.

The F-35B — a fighter jet capable of short takeoffs and vertical landings — would be used on navy vessels originally designed to carry helicopters. The reports come amid increasing threats from nuclear-armed North Korea and as China modernizes its armed forces and demonstrates growing maritime ambitions in the region.

"The F-35 can be considered both a deterrent and also carry the fight to a potential adversary," said Seth Cropsey, a former deputy undersecretary of the Navy in the Reagan and Bush administrations and now a senior fellow at the Hudson Institute.

The so-called jump-jet stealth F-35B fighter could add more firepower for the U.S. allies and potentially help find, track and attack enemy aircraft and missiles as well as perhaps conduct strike missions deep inside North Korea, according to experts. To be clear, other surveillance assets also would likely be used to support attacks in enemy territory.

Japan and South Korea are among the 13 countries involved with the F-35 Joint Strike Fighter program, which has three variants — the U.S. Air Force's F-35A (conventional takeoff and landing version), the F-35B (the U.S. Marine Corps variant that can land without conventional runways) and the F-35C (the U.S. Navy version with larger wings, special landing gear for aircraft carriers and greater fuel capacity).

Lockheed Martin is the prime contractor on the F-35 Joint Strike Fighter program.

John Pike, a military analyst at Globalsecurity.org, said the F-35B would give the South Koreans stronger fleet air defenses and formidable ship-to-shore ground attack capabilities "that you wouldn't want to mess with."

Furthermore, he said, putting the versatile fighter on a mobile platform at sea would make it harder to destroy than if the plane were at an airfield.

Japan reportedly wants to use the F-35B, a fifth-generation fighter costing more than $100 million apiece, for its Izumo-class helicopter carriers, the country's Kyodo news agency reported this week.

Japan's reported interest in using warships to launch the F-35B isn't sitting well with Beijing, which this year went operational with its own fifth-generation fighter with stealth capabilities. China also is preparing to move forward with its third aircraft carrier and has an advanced "carrier-killer" missile capable of threatening U.S. aircraft carriers in the Asia-Pacific region.

"We urge Japan to do more that may help enhance mutual trust and promote regional peace and stability," Hua Chunying, a Chinese Foreign Ministry spokesperson, was quoted as saying Tuesday in state media. She also said such actions by Tokyo would violate Article 9 of Japan's 1946 constitution, which renounces war and technically the use of force.

Regardless, Tokyo has seen tensions increase in recent years with Beijing due to maritime disputes, including over islands in the East China Sea and the communist country's aggressive actions in the South China Sea. As a result, the Japanese Maritime Self-Defence Force has been rethinking its security strategy and strengthening its capabilities.

Experts expect China to continue building up its military forces in the South China Sea in 2018, adding to bases, radar and weapons capabilities on several artificial islands. The new U.S. National Security Strategy released last week by President Donald Trump stated that China's "efforts to build and militarize outposts in the South China Sea endanger the free flow of trade, threaten the sovereignty of other nations, and undermine regional stability."

At present, Japan only has the F-35A — the conventional takeoff and landing variant — but is considering whether to purchase the F-35B fighter. Japan took delivery of its first F-35A in 2016 and is assembling more than three dozen others domestically at a facility in the Nagoya area.

Meantime, South Korea also is looking at the F-35B for use aboard a roughly 14,000-ton warship scheduled to get deployed in 2020. The plan would be to essentially refit the so-called Dokdo-class vessel to become medium-sized aircraft carrier. Seoul already has a Dokdo-class amphibious assault ship in operation.

"I understand that the military top brass have recently discussed whether they can introduce a small number of F-35B fighters and operate them aboard the new ship that has already been deployed and one to be additionally built," South Korea's Yonhap News Agency reported this week, quoting an unidentified military source.

According to the source, Seoul is considering the stealth fighter as part of "maximizing the strategic value" of its newest amphibious landing ships.

South Korea already has agreed to buy 40 F-35As and expects to deploy the first ones next year. The Seoul government also is reportedly looking at adding the F-35B to its planned purchases of aircraft over the next several years.

Cropsey said the F-35B, though, should be viewed as part of a larger defense strategy and not in isolation.

"As a weapon in the toolbox it's a good one," the former Pentagon official said. "But for as good a plane as it is, there's no assurance of getting all the targets. There's no assurance that the planes can get through the air defenses or that the strikes against the targets will come in time."

Pike, however, is optimistic about the F-35's stealth capabilities being able to penetrate North Korea air defenses.

"I just don't think that North Korea's air defenses are much to worry about," said Pike. "As far as the stealth fighter is concerned, it would be like a hot knife through butter."

Pike said the F-35B could attack ballistic missiles on the ground in North Korea, especially since Pyongyang has been relying mostly on liquid fuel for missiles — and that fueling process can take time and slows down launch time.

Some also have suggested the advanced sensors and air-to-air missiles on the stealth fighter could be capable of killing ballistic missiles launched during the boost phase. Experts suggest that the scenario may not be entirely practical and that it would make more sense to take out the missile before it's launched.

Either way, shooting down a North Korean missile on the launch vehicle or in the boost phase comes with huge risks. It could spark a bloody war with the North firing rockets into the greater Seoul area, where about half of the South Korean population lives. And, there's a chance the regime could use chemical weapons or even launch nuclear-tipped missiles.

Last month, North Korea test-launched its new intercontinental ballistic missile, the Kwasong-15, from a so-called transporter-erector-launcher (TEL). The missile range and height appear to have showed that North Korean leader Kim Jong Un has an ICBM capable of reaching most, if not all of, the United States.

The "window of vulnerability" happens before the ballistic missile gets fired from the launchers, which are essentially timber trucks converted to carry and launch weapons. The ballistic missiles on these launchers must be first lifted into an upfront firing position before the liquid fuel can be loaded. That could take an hour os so, experts said.

Pike is confident the U.S. and its Asian allies could monitor large swaths of North Korea's flat terrain where the TEL missiles could possibly be launched and spot something "pretty quick." Signs of an ICBM or another ballistic missile launch would in part come from "a caravan" of vehicles, including fuel trucks, as they move toward the TEL with the missile, the analyst said.

"We cannot assume that we're going to see a 12-vehicle convey strung out on a highway coming out of a tunnel, all nice and lined up," said Pike. "That would be too easy. The elements of the convoy are going to be dispersed, and you will have a 'flash mob' of a dozen vehicles converging simultaneously at a pre-arranged location. So it's only when the 'flash mob' assembles that the 'kill chain' will perk up."