New Delhi: With an aim to improve the cooperation between US and Indian maritime forces, Indian naval ships on Monday conducted a passage exercise (PASSEX) with the United States Navy's USS Nimitz carrier strike group near the Andaman and Nicobar islands as it is transiting the Indian Ocean. USS Nimitz is returning from the South China Sea, where it arrived with another US Navy ship Ronald Reagan to conduct dual-carrier operations. The exercise assumes importance amid India's strained ties with China. Lt. Cmdr. Liza Dougherty, the warship's spokeswoman, confirmed that the Nimitz Carrier Strike Group is participating in cooperative exercises with the Indian Navy in the Indian Ocean commencing July 20.