(CNN) A decisive election win for Japanese Prime Minister Shinzo Abe boosts one of US President Donald Trump's strongest allies in Asia as both Washington and Tokyo grapple with how to handle Pyongyang.

Abe, a conservative hawk, has long been a supporter of Trump's more aggressive North Korea policy, which has coincided with his attempts to rewrite Japan's post-war pacifist constitution.

Following Sunday's vote, Japanese Defense Minister Itsunori Onodera warned the threat from North Korea -- which has repeatedly fired missiles over Japan in recent months -- had reached an "unprecedented, critical and imminent" level.

The US, South Korea and Japan need to collectively trial "different responses" for tackling the regime, Onodera told a meeting of the countries' military officials Monday.

Trump ties

Trump and Abe have shared a strong relationship since before the US President was inaugurated, with Abe traveling to Trump Tower in New York to meet with Trump while Barack Obama was still in office.

During that "unofficial" meeting , Trump's first with any world leader, Abe hailed the US-Japan alliance and said he wanted to "build trust" with the new President.

Their initially strong relationship was strengthened during Abe's second visit to the US, when at Trump's Florida resort Mar-a-Lago, North Korea fired an intermediate-range ballistic missile , the first since Trump's inauguration.

As the North Korea issue has escalated and come to dominate Trump's first year in office, Abe has largely supported the White House's increasingly aggressive, hawkish line on Pyongyang.

"Trump sees Moon as more acquiescent (towards Pyongyang) on some of the key questions as regards the North," said Alex Neill, a senior fellow at the Shangri-La Dialogue.

Euan Graham, director of the International Security Program at the Sydney-based Lowy Institute, said Washington views Abe as "probably as good as it gets in terms of security cooperation from a Japanese leader."

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Constitutional crises

One of Abe's long-term goals has been to change the Japanese constitution to remove restrictions on the country's military, known as the Self Defense Forces.

Those forces are among the best equipped in the world , but some say they're hampered by Article 9 of the constitution , which saw the country "renounce war as a sovereign right of the nation and the threat or use of force as means of settling international disputes." Abe has voiced support for strengthening SDF but not yet repealing Article 9.

Rewriting that article is a "personal priority for Abe and a conservative cohort around him," Graham said, though support for it remains low among the Japanese public.

"Kim Jong Un has been very good news for Abe in political terms, by allowing him to play the security card during the election," Graham said, referring to the North Korean leader.

Changing the constitution could affect Japan's North Korea policy by, for example, allowing it to shoot down missiles headed for the US as they pass over Japan, or launching a pre-emptive strike on North Korean territory, both of which may be illegal under the current wording.

"Prospects for peaceful resolution with North Korea are becoming more slim, strengthening Abe's case for building out Japan's offensive capabilities," Nicole Freiner, a Japan specialist at Bryant University, wrote Tuesday

Neill also predicted Japan could seek to actively build up its military deterrence, discouraging North Korea from taking action rather than simply reacting to that action defensively.

Next month, 12 US F-35A Lightning II stealth fighters will be deployed to Japan for a six month rotation. Some experts have previously criticized the jets' presence in North Asia as potentially destabilizing, as the only way North Korea can defend against them is via a preemptive strike.

What about China?

Memories of Japan's brutal imperial past, during which the country occupied many neighboring countries and massacred civilians, are strong in Asia, and Freiner predicted a move by Tokyo toward greater military spending on offensive capabilities could "spell trouble for peace" in the region.

Beijing in particular has been a strong critic of attempts to change the Japanese constitution, and Neill predicted any move to do so could lead to a repeat of the 2012 crisis over the Japan-controlled Senkaku Islands, called the Diaoyu Islands by China.

A territorial dispute over the island chain -- which lie between Okinawa and Taiwan in the East China Sea -- has been ongoing for decades, sparking violent protests in China and tense stand offs between the countries' air and naval forces

"China drew a line (in 2012) and started massively ramping up its armaments and maritime saturation of the region," he said.

"If Japan moved toward changes to the constitution I think you'd see something similar."