WASHINGTON: Invoking a range of concerns from immediate niggles such as systems interoperability to long-term worries over strategic partnership choices, the Trump administration is once again seeking to persuade India to ditch buying the Russian S-400 missile defence system.A senior administration official’s testimony before Congress on Thursday was aimed at New Delhi as much as US lawmakers, ahead of a visit to India later this month by Secretary of State Mike Pompeo and a meeting between President Trump and Prime Minister Narendra Modi in Osaka on the sidelines of the G-20 summit."At (a) certain point a strategic choice has to be made about partnerships and a strategic choice about what weapons systems and platforms a country is going to adopt," acting US assistant secretary of state Alice Wells told a House Foreign Affairs Subcommittee in a hearing on "US Interest in South Asia and FY 2020 Budget."Notwithstanding several wrinkles on the trade and commerce front, Wells offered an upbeat assessment of the current US ties, pointing to increased defence ties and military purchases, while pledging to sell ever more sophisticated hardware if New Delhi canned the purchase of the S-400 system it has already contracted to buy from Russia."Under the Trump administration, we've been very clear that we're ready to help meet India's defence needs and we are seeking a very different kind of defence partnership building on the 'Major Defence Partner' designation that India has received from Congress," Wells said, cautioning that New Delhi’s purchase of the S-400 missile defence system would limit cooperation. US officials have also voiced concern over interoperability issues with American systems if India continues with its large inventory of Russian platforms.US officials in recent weeks have indicated that Washington is ready to sell India platforms such as its top-of-the-line Terminal high Altitude Area defence (THAAD) and Patriot-3 missiles defence systems if New Delhi ditched the S-400.Wells also drew a picture of broader strategic cooperation and partnerships in what the Trump administration calls the Indo-Pacific region, pointing out that just a few weeks ago, India, the United States, the Philippines and Japan did a sail by in the South China Sea."In both our bilateral, trilateral, quadrilateral formats, we're working together in ways that we didn't even conceive of 10 years ago. And so we'd like all aspects of our military relationship to catch up to this new partnership," she said.President Trump, Prime Minister Modi, and Japanese Prime Minister Shinzo Abe are scheduled to have a trilateral meeting in Osaka in what analysts see as a Washington effort to build partnerships to contain a rising China.The constant US harangue on the need for India to forgo buying the S-400 comes amid a raft of punitive American measures against New Delhi despite the professed mutual desire to develop a strategic relationship.From squeezing India to stop buying oil from Iran to withdrawing preferential trade access to New Delhi to ever-tighter norms on guest worker visas to President Trump’s constant cribbing over a minor tariff issue relating to Harley Davidson motorcycles, the Trump administration, in New Delhi’s view, acts in ways that undermine the mutual pledge to elevate the relationship.Still, Wells maintained that it was New Delhi’s protectionism and tariff barriers that was the irritant, even as Prime Minister Modi was lashing out in a speech at the Shanghai Cooperation Organisation in Bishkek at unilateral trade protectionism and calling for a "rule-based, transparent, anti-discriminatory, open and all inclusive WTO-centered multilateral trading system focused so that the interests of every country specially the developing ones can be taken care of."