TOKYO - Japanese Prime Minister Fumio Kishida, in a policy speech on Monday (Dec 6), said he will conduct a sweeping review of the country's defence policy amid a volatile security climate.

He also listed other priorities during the speech in Parliament, including fortifying the economy against global inflation by ensuring that wages were raised to protect livelihoods and boost consumption.

On Covid-19, he said that his duty was to "prepare for the worst", even if his policy measures were seen as an overreaction by history.

Japan has imposed among the world's strictest border restrictions to keep out the Omicron variant, with all non-resident foreigners barred from entering the country unless in exceptional cases.

"I am prepared to bear all the criticism that we are being too cautious when we do not yet fully understand the situation," Mr Kishida told the Diet on Monday, at the start of an extraordinary session that will close on Dec 21.

"The people entrusted me with the responsibility to proceed with my work with such determination."

Mr Kishida, 64, is expected to spar on policy with Mr Kenta Izumi, 47, who last week was elected leader of the main opposition Constitutional Democratic Party of Japan, in the current Diet session.

In one of the longest policy speeches before the Diet in recent years - running at nearly 9,000 words and clocking 35 minutes - Mr Kishida spelt out his policy vision in explaining why his government was seeking a record supplementary budget of 35.9 trillion yen (S$434 billion) this year.

The significant outlay, which is part of an overall economic stimulus package amounting to 55.9 trillion yen, comes despite Japan having the worst debt-to-gross domestic product ratio among advanced economies.

But Mr Kishida said it was necessary to jump-start a virtuous circle of growth, which he stressed "must come before fiscal reform".

The sum includes a request of 773.8 billion yen in extra defence spending for the current fiscal year ending in March, bringing the overall budget to a record 6.1 trillion yen.

Japan plans to buy new missile batteries, maritime patrol planes, and air-to-air missiles, among other things.

Mr Kishida said on Monday that it was not only high time for Japan to debate the need to revise the war-renouncing Constitution for the first time since its enactment in 1947, but also to consider acquiring weapons for the pre-emptive strike on enemy bases.

Japan's Defence Ministry has singled out China as a key threat to Japan's security, with former prime minister Shinzo Abe raising eyebrows when he said last week that Japan will act if China were to take Taiwan by force.

Mr Kishida also cited his signature "new style of Japanese capitalism" platform that led his Liberal Democratic Party to win resoundingly in a general election on Oct 31, stressing that economic growth must come before fiscal reforms.

He saw wage hikes as a key policy plank to overcome years of deflation and weak consumer spending, especially amid a global oil and supply chain crisis.

He went further than his predecessors such as Mr Yoshihide Suga and Mr Abe in dangling "drastic" tax breaks and subsidies for companies with revenues at pre-pandemic levels to increase wages by at least 3 per cent.

He also spoke about economic security - "an issue that must be seen as an investment for the future and not a current cost" - as he vowed lavish spending to boost research and development to drive new areas of innovation in vaccine development to artificial intelligence, life science and space.

Tougher laws will be tabled in the Diet next year to make supply chains more resilient against the strategic theft of intellectual property, said Mr Kishida.

Still, he devoted a significant portion of his speech towards Covid-19, even though Japan now routinely registers fewer than 200 cases a day.

He vowed to fast track the roll-out of vaccine booster shots with 77 per cent of the population already having received both doses, while noting that measures must be taken to make the healthcare system more robust in case of a sixth wave.

"The time to repair the roof is when the sun is shining," he said, citing former United States president John F. Kennedy in stressing his belief of the need to "prepare for the worst" rather than be caught off guard.