The U.S. and India have a shared interest in supporting freedom of navigation and free, fair and reciprocal trade, as well as the peaceful resolution of disputes in the Indo-Pacific, according to one of the senior defense officials, who spoke on background to discuss sensitive bilateral conversations.

To the extent that China or anybody else would want to undermine those principles or challenge those principles, thats part of how you build these relationships and build these networks to provide balance to that or to stand up against it, the person said.

Austins arrival in New Delhi marks the third stop on his first overseas trip as Pentagon chief and comes after visits to Japan and South Korea for meetings with Secretary of State Antony Blinken and their Japanese and Korean counterparts. After his discussions with Modi, Austin will meet with India’s national security adviser, the senior defense official said. On Saturday, Austin will sit down with the ministers of defense and external affairs.

The U.S. has sought for years to strengthen its partnership with India through increased military cooperation, particularly with the Indian Navy, and arms sales. But one snag could be Indias purchase of the advanced Russian S-400 missile system. The U.S. imposed sanctions on NATO ally Turkey for its own purchase of the S-400 under the Countering Americas Adversaries Through Sanctions Act, but has not yet penalized India for the same acquisition.

Indias potential operation of the S-400 would pose a problem for the U.S.; the system was designed to detect and target advanced U.S. fighter jets such as the F-35.

The senior defense official declined to say whether the U.S. was weighing sanctions over the S-400, but noted that the system has not yet been delivered to India, an event that would likely trigger penalties.

Buying U.S. equipment is not a condition for advancing cooperation, our advancing cooperation is based on a converging of strategic interests, the senior defense official said, adding that buying equipment that can operate together “is certainly a means to be able to operationalize that partnership.

Another senior defense official declined to comment on whether Austin would speak with Indian officials about Modis harsh treatment of Indias Muslim population, but said we routinely raise issues of human rights.

The goal in the Indo-Pacific is to build the existing hub-and-spoke bilateral relationships between the different countries into more of a network set of overlapping relationships that can do a better job sharing information and cooperating on military operations, the senior defense official said.

Its going to look very different than the NATO alliance, the person said. Its going to look very unique; its going to be something that fits with how the Indo-Pacific has evolved.