Washington has been urging New Delhi to sign a 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,” Carter said after talks with his Indian counterpart, Manohar Parrikar.
Carter said the two sides would finalise the text of an agreement in coming weeks.
India has had concerns that a logistics agreement would draw it into a military alliance with the US and undermine its traditional autonomy.
But Indian 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.
India is keen to access US technology for Modi’s “Make in India” plans to build a domestic industrial base, including the defence, and cut expensive arms imports.
Carter said the two countries would also soon conclude a commercial shipping information exchange agreement.
The US military has made clear it wants to do more with India, especially in countering China.
Carter is on his second visit to India in less than a year, aimed at cementing defence cooperation in the final months of Barack Obama’s presidency.
Carter said the two countries were advancing collaboration in aircraft carrier design and technology, potentially the biggest joint project since they launched a Defense Technology and Trade Initiative (DTTI) in 2012.
India, which operates a re-tooled Russian carrier, plans to build its biggest indigenous carrier, for which is it looking at US electro-magnetic technology to launch heavier aircraft.
“We have decided to take forward discussions under DTTI more aggressively on key areas such as jet engine technology. We will also continue our very useful and productive discussions on cooperation… on aircraft carriers,” Parrikar said.