Japan on Tuesday relaxed its long-standing ban on the export of weapons and military equipment, a move that is expected to boost ailing Japanese defense companies and create opportunities for international projects.

The change, coming after more than a year of government discussion, reflects concern that Japan has fallen behind in weapons development, with its major companies unable to mass-produce and sell their technology abroad. It also helps the country at a time when the government has trimmed its budget for weapons procurement, despite regional threats from China and North Korea.

The move, welcomed in Washington, allows Japan to take part in joint development projects on everything from fighter jets to missile defense systems. It also allows the country to supply equipment for humanitarian purposes.

The export ban dates back to 1967, when Japan established its so-called “three principles” prohibiting arms deals with communist countries, countries subject to U.N. sanctions and countries engaged in international conflicts. Several years later, Japan tightened the principles into a de facto ban on all exports.

Even after Tuesday’s decision, the three original principles remain in place, a government spokesman said. But even a slight change in the weapons ban is likely to trigger unease in a nation that considers the restriction a pillar of its pacifist image.

“Concerns persist . . . about whether Japan can prevent weapons and related technology from being leaked to strife-torn countries or terrorist groups,” Japan’s Kyodo news agency said in its report.

This month, Tokyo selected the U.S.-made F-35 Lightning II JSF as its new stealth fighter. In the coming years, Japan will purchase 42 jets, and the first four fighters will be produced and assembled overseas. The government expects, however, that some parts for the rest of the fighters will be produced domestically. With the relaxation on the weapons ban, contractors such as Mitsubishi Heavy can compete as long-term suppliers for some of the fighter’s components.

Because of the ban, “Japan has been suffering from low economy of scale, as it was very expensive to produce arms,” said Narushige Michishita, an assistant professor at the National Graduate Institute for Policy Studies. “Because Japan had to be self-sufficient in producing arms, Japanese tanks cost three times more than the U.S.-made ones. It was a huge economic burden to the Japanese.”

Ayako Mie contributed to this report.