U.S. President Donald Trump had turned down India's invitation to be the chief guest at next year's Republic Day parade, local television news channel News18 reported on Sunday.

The television channel quoting sources said the U.S. authorities conveyed Trump's decision in a letter to Indian Prime Minister's National Security Advisor (NSA) Ajit Doval recently.

"The U.S. president's domestic commitments, including his State of the Union address, around that time seems to have been the reason for declining the invitation. In the letter, Trump is said to have regretted his inability to accept the invitation," News18 said.

India officially sent the Republic Day invitation to the U.S. president in April this year.

Ties between New Delhi and Washington have recently been under a lot of strain in view of India's defence purchases from Russia and the oil imports from Iran.