US Defense Secretary Leon Panetta flies to India on Tuesday for talks focusing on Washington's strategic shift towards Asia, as US officials eye New Delhi as a potentially pivotal partner.

Security ties to India have steadily improved in recent years but US officials have yet to realise the goal of a game-changing alliance that could check China's role and empower the two countries' economies, analysts say.

During his two-day visit, Panetta is expected to discuss expanding defence ties, the NATO war effort in Afghanistan and China's increasing economic and military power in the region, US officials said.

Panetta is due to meet Prime Minister Manmohan Singh and National Security Adviser Shiv Shankar Menon on Tuesday afternoon along with other officials, before giving a policy speech on Wednesday, officials said.

In President Barack Obama's new strategy blueprint unveiled in January, India is the only country mentioned by name as a vital partner.

US officials say the two countries share democratic traditions and similar concerns about China's stance as well as the threat posed by Islamic extremists in South Asia.

"Strategically, we see India as a partner with a lot of common interests," a senior defence official said on condition of anonymity.

But both countries have been disappointed about a lack of progress on defence trade and other fronts.

Although US arms sales to New Delhi have dramatically expanded over the past decade, India in April rejected bids by US contractors for a $12 billion fighter jet contract, leaving only France's Dassault and the Eurofighter consortium in the running.

India, for its part, has expressed irritation over US export restrictions that prevent it from gaining access to some high-tech US weaponry.

On the war in Afghanistan, India worries that the departure of most US and NATO forces by the end of 2014 could empower Islamic extremists.

Last week, India called for greater coordination with the United States on Afghanistan.

Although India favours improving military relations with the United States, New Delhi has opted to place limits on the arrangement, giving it room to manoeuvre, analysts said.

"India is unwilling to tightly align with US objectives, and it is presently mired in political sclerosis and an economic slowdown," said Patrick Cronin, senior adviser for the Center for a New American Security, a Washington-based think tank.

The US-India security relationship has generated increased cooperation between the two countries' navies, as well as more intelligence sharing.

"Naval cooperation (with the United States) is one of the chief tangible benefits, and the number of bilateral and trilateral exercises with India remain at a record high," Cronin said.

The India trip, part of a nine-day tour of Asia, follows stops in Vietnam and Singapore in which Panetta signalled US plans to bolster its naval presence in the face of a more assertive China.

In Vietnam, Panetta became the first Pentagon chief to set foot in Cam Ranh Bay, a major port and airfield for US forces during the Vietnam War.

Standing on the deck of a US naval supply ship undergoing repairs at Cam Ranh, Panetta described the deep-water harbour as a strategically valuable port that could support the US military's rebalance towards the Pacific.