India's new Prime Minister Narendra Modi will likely visit Japan next month, the foreign ministry said Friday, in a boost for Tokyo as it looks to shore up regional alliances and counter an increasingly assertive China.

Modi, whose Hindu nationalist Bharatiya Janata Party won a landslide victory in May's elections, is set to make his maiden foreign trip as premier to neighbouring Bhutan later this month.

Foreign ministry spokesman Syed Akbaruddin said that while the (South Asian) "neighbourhood remains India's priority", Japan has offered to host Modi soon and he will likely take up the invitation in July.

Modi's first trip to the United States, meanwhile, will "most likely" be in September, Akbaruddin added.

The world is closely watching Modi's first moves as leader of the world's biggest democracy, and a visit would be a boost for Japanese Prime Minister Shinzo Abe as he seeks to raise Asian support to counter China's increasing regional assertiveness.

New Delhi, like Tokyo, has a long-running territorial dispute with Beijing, whose growing military confidence is causing disquiet in Asia and beyond.

China is in a row with Japan over ownership of several islands in the East China Sea, and at odds with India over a long-running border dispute that flared into a brief war in 1961.

The Asian giant is also locked in tense maritime territorial rows with neighbours in the South China Sea, which Beijing claims almost in its entirety.

The United States, Japan's key ally, is concerned about China's growing economic and military clout and would welcome a closer relationship between New Delhi and Tokyo, which geographically bookend Beijing.

- Growing trade partner -

Trade between India and Japan has steadily increased over the last decade, with the pair signing a free trade pact in 2011.

Modi swept to power on a pledge to invigorate India's sluggish economy, whose more-than-billion-strong population promises a huge potential market.

With its decrepit roads and other infrastructure, India is also a natural market for Japan's huge infrastructure firms and has been the recipient of frequent development aid and loans.

Japanese media had suggested that Modi could visit as early as this month, with the increasingly precarious Asian security situation high on the agenda, along with a potential deal on nuclear power technology.

"Prime Minister Abe has invited new Prime Minister Modi to visit Japan, and the two countries are making final adjustments for that," Japanese government spokesman Yoshihide Suga told reporters in Tokyo on Friday.

Abe and Modi exchanged friendly greetings on Twitter after his landslide win. The new Indian leader visited Japan twice before coming to power, in 2007 and in 2012.

Modi's first trip to the United States as prime minister, meanwhile, will not take place until later in the year.

Washington's ties with Modi have been complicated by a US ban on him travelling to the country after deadly 2002 anti-Muslim riots swept the western state of Gujarat where he was chief minister for more than a dozen years.

Modi, accused by rights activists of turning a blind eye to the bloodshed, has never been found guilty of any wrongdoing by an Indian tribunal in connection with the riots.

Analysts have suggested the previous anti-Modi mood in Washington might hamper future friendship between the two countries.

Modi has displayed no rancour publicly about the visa ban by Washington, telling an interviewer before his election that foreign relations "should not and cannot be influenced by incidents related to individuals".

The US State Department has said that Modi will face no problems visiting the United States as prime minister because he will receive a special A-1 visa as a head of government.