Japan’s defense budget for the next fiscal year is set to top 5 trillion yen (USD 40 billion) for the first time ever, government sources say.

According to the Japanese government sources, the budget for the 12 months from April 2016 would include funding for relocation of a controversial US military base in southern Okinawa Island. The base is host to the bulk of US military forces in Japan.

The 2016/17 budget will also be used to fortify an island chain in the East China Sea, close to the territory which is also claimed by Beijing.

The budget is expected to be finalized by the cabinet in late December. If approved, it would be the fourth consecutive rise in military spending since Japanese Premier Shinto Abe took office in 2012.

The huge raise comes months after Japan's parliament enacted hotly-contested legislation that allows its defense forces to prepare for an expanded role overseas.

On September 19, Japanese lawmakers in the upper house of the parliament approved the law, following hours of heated debates.

A screen grab from a Ruptly video shows Japanese people protesting a controversial law that expands the role of the country's military in Tokyo, September 23, 2015.

The legislation allows Japan’s army, the so-called Self-Defense Forces, to be deployed abroad in combat operations for the first time since World War II. The law will broaden the mandate of Japan’s military forces, allowing them to participate in foreign operations in order to protect allies, including the United States, even if there was no direct threat to Tokyo.

The government of Prime Minister Abe says the legislation is required to deal with a changing security environment and threats posed by regional countries that are expanding their military and nuclear capabilities.

Opponents, however, say the legislation would damage 70 years of pacifism as the revisions would alter the 1945 constitution, which bars Tokyo from combat except in self-defense.