TOKYO (AFP) -- Conservative soulmates Narendra Modi and Shinzo Abe declared Monday ties between India and Japan were moving to a "new level", during a summit pregnant with promise for a relationship they hope will offer a counterweight to China.

Modi's first foreign visit outside the Indian sub-continent has been a relaxed display of personal chemistry between the leaders of countries that bookend an ever-more assertive Beijing, and which both have prickly relations with their giant neighbour.

Despite falling short of launching a "two-plus-two" security framework of foreign and defence ministers, the two men hailed the transformative potential of the partnership between Asia's second and third largest economies.

"The world knows the 21st century is Asia's century," Modi told a joint press conference after the summit.

"But its shape and quality are not yet clear. This will be decided by how Japan and India work together," he said, adding: "I think our relationship is moving to a new level."

Abe also lauded a tie-up he said was "the one with the most potential in the world".

"Together, working hand-in-hand with Prime Minister Modi, I intend to fundamentally strengthen our relationship in every field to elevate our relationship to a special strategic and global partnership," he said.

Both nations are wary of China's growing ambition to be seen as the regional keystone and are keen to curb its activity in the East and South China Seas and in the Indian Ocean.

Tokyo and New Delhi have separate long-running territorial disputes with Beijing, which is widely seen as having pushed its claims more aggressively in recent years.

Underlining the point, Chinese coastguard ships briefly sailed into waters off the Japanese-controlled Senkaku islands on Monday, officials said. China calls the islands the Diaoyus.

While neither man directly addressed the Chinese elephant in the room, Modi left little doubt it weighed heavy.

At a speech to business leaders earlier in the day, he lambasted the expansionism of yesteryear and said it was not a viable model for Asia.

"There are 18th-century-style ways and thinking that involve expanding (geographically) by taking away the land of another nation and going into the seas," he said through a translator, without making any specific reference to modern-day China.

"If Asia is to become the leader in the 21st century, Japan and India should lead" and promote a path of peaceful development, he said.

Washington is eager for the two countries to step up their cooperation by way of offering a regional balance to China, at a time when its own military commitment around the world is being questioned.

In a joint statement after their summit in Tokyo, Modi and Abe said they were pleased at recent three-way cooperation involving the US.

"(We) hope that this would lead to concrete and demonstrable projects to advance... shared interests and those of other partners," the statement said.

"(We) decided to explore holding this dialogue among... (the three) foreign ministers (and) explore the possibility of expanding at an appropriate time... consultations to other countries in the region."

Following a recent relaxation of self-imposed restrictions on weapons exports, Japan is keen to boost its military industry, notably with a possible future deal on the supply to India of US-2 amphibian aircraft.

The leaders "directed their officials to launch working-level consultations between the two countries with a view to promoting defence equipment and technology cooperation".

Economic relations also received a fillip, with an intended 3.5 trillion yen ($34 billion) in public and private investment and financing from Japan over five years.

That figure, which marks a doubling of present levels, includes a 50 billion yen loan for infrastructure development for a country where transport links, power production and telecommunications systems can be shaky and unreliable.

There was also agreement on the joint development of rare earths, which are vital for high-tech manufacture. Their production is dominated by China.

Modi was greeted in the ancient city of Kyoto on Saturday by Abe, who dispensed with the formal handshake that starts most such visits in favour of a bear hug.

The pair -- both economic liberals and staunch nationalists -- have met on several occasions, and are thought to enjoy a personal warmth that is notably absent in Abe's dealings with US President Barack Obama.