India and the US have agreed in principle to share military logistics, US Defence Secretary Ashton Carter said on Tuesday, as both sides seek to counter the growing maritime assertiveness of China.

Washington has been urging New Delhi to sign the Logistics Support Agreement that allows the two militaries to use each other's land, air and naval bases for resupplies, repair and rest.

But after years of dithering, the two sides said an agreement was in hand, although not yet ready for signing.

"We have agreed in principle that all the issues are resolved. We now need to finalise the draft," Carter said after talks with his Indian counterpart, Manohar Parrikar.

New Delhi has had concerns that the logistics agreement will draw it into a military alliance with the US and undermine its traditional autonomy.

But Prime Minister Narendra Modi's administration, faced with an assertive China expanding its influence in the South China Sea and into the Indian Ocean, has signalled its desire to draw closer to the US. China is also a close ally of India's arch-rival, Pakistan.

New Delhi is keen to access US technology for Modi's "Make in India" plans to build a domestic defence industrial base and cut expensive arms imports.

Carter said the two countries would also soon conclude a commercial shipping information exchange agreement.