WASHINGTON, June 21 (Reuters) - U.S. President Joe Biden welcomes India's prime minister, Narendra Modi, on Wednesday for two days of talks that the White House sees as bolstering "one of the defining partnerships of our age," despite ongoing concerns about human rights. Washington wants India to be a strategic counterweight to China while Modi is seeking to raise the influence that his country, now the world's most populous, has on the world stage. Biden and Modi are expected to announce a variety of agreements related to defense cooperation and sales, artificial intelligence, quantum computing and investments in India by...