India and the United States are closing in on an agreement to share military logistics after 12 years of talks, officials said, a sign of strengthening defense ties between the countries as China becomes increasingly assertive.

The United States has emerged as India’s top arms source after years of dominance by Russia, and holds more joint exercises with it than any other country.

It is in talks with New Delhi to help build its largest aircraft carrier in the biggest military collaboration to date, a move that will bolster the Indian navy’s strength as China expands its reach in the Indian Ocean.

After years of foot-dragging by previous governments over fears that the logistics agreement would draw India into a binding commitment to support the United States in war, Prime Minister Narendra Modi’s administration has signaled a desire to move ahead with the Logistics Support Agreement (LSA).

That would allow the two militaries to use each other’s land, air and naval bases for resupplies, repair and rest, officials said.

Admiral Harry Harris, head of the U.S. Navy’s Pacific Command, said the two sides were working on the LSA, another agreement called the CISMOA for secure communications when the militaries operate together, and a third on exchange of topographical, nautical, and aeronautical data.

“We have not gotten to the point of signing them with India, but I think we’re close,” Harris, due in India this week, told the U.S. House Armed Services Committee on Wednesday.

The progress comes as the countries consider joint maritime patrols that a U.S. official said could include the South China Sea, where China is locked in a territorial dispute with Vietnam, the Philippines and Taiwan among others.