Japanese Prime Minister Shinzo Abe, concerned about China's rising military spending and disputes with Beijing over islands in the East China Sea, has signed a partnership deal with Nato.
The accord, signed by Abe and Nato Secretary General Anders Fogh Rasmussen on Tuesday during Abe's visit to the bloc's Brussels headquarters, will deepen Japan's co-operation with the Western alliance in areas such as counter-piracy, disaster relief and humanitarian assistance.
After addressing ambassadors from the 28 Nato nations, Abe drew a parallel between the situation in Ukraine, where Russia has annexed Crimea, and Asia, in an apparent allusion to a Sino-Japanese stand-off over islands in the East China Sea known as the Senkakus in Japan and the Diaoyus in China.
"We will not tolerate any change of status quo through intimidation or coercion or force. This is not only applicable to Europe or Ukraine. This is applicable to East Asia and it is applicable to the whole world," Abe said.
Abe urged Russia and political parties in Ukraine to recognise the legitimacy of Ukraine's May 25 presidential election.
"At the same time, in order to resolve this problem, we have to have dialogue with Russia."
Nato has said it would not get involved militarily in Ukraine but it has reinforced security in eastern European members of the bloc that are worried by Russia's renewed assertiveness.
In addition to steps it had already taken to increase its forces in Eastern Europe, Nato would "not hesitate to take further steps if necessary to ensure effective defence and protection of our allies", Rasmussen said.
Abe, who made his first visit to Nato headquarters in 2007, has long been interested in strengthening Japan's relations with the US-dominated alliance.
Analysts say Japan's aim is to increase diplomatic support over its security concerns, particularly China's military build-up and North Korean missile launches and nuclear tests.
"Japan does not actually expect Nato to play a direct military role in the Asia-Pacific region, but it does expect allies to share perceptions and approaches," Michito Tsuruoka, a senior research fellow at Japan's National Institute for Defence Studies, wrote in a paper for the Nato Defence College last year.
Tension between Japan and China spiked last year when Beijing announced an air-defence zone over a wide area including the disputed islands.
Abe told Nato ambassadors he believed Japan should play a more active role in defending the freedom of overflight and navigation in the region.
With its operations in Afghanistan coming to an end and Russia flexing its muscles, Nato is now expected to refocus on its core mission of defending its territory, a trend that may not be welcome to Japan and other partners outside Nato's area.
Abe's priority has been to revive a long-sluggish economy, but he has also pledged to strengthen Japan's military and boost its security profile to meet what he says is a threat from China's rapid military build-up.
Abe also aims to lift Japan's ban on collective self-defence, which means helping an ally under attack, to bolster security ties with the United States.
Rasmussen said Nato welcomed Japan's steps "to become a pro-active contributor to peace".
"We share interests in countering piracy, countering terrorism. We share interests in disarmament," he said.