United States President Donald Trump has turned down India’s invitation to be the chief guest at the 70th Republic Day celebrations, several media reports said on Sunday. The White House has reportedly expressed regrets to the Narendra Modi government for Trump’s inability to travel to India in January, citing the US president’s “crowded calendar”, The Hindu reported.

Trump’s pressing domestic commitments, including the State of the Union address – likely to be held between January 21 and 29 – have been cited as the reason for not accepting the invitation, according to Mint.

“We always knew this would be a difficult visit to get a firm decision on, as the date for India is non-negotiable,” an unidentified Indian official told The Hindu. “As a result, we didn’t take it past the initial rounds of discussions, and left it to the US government to work out.”

In August, White House Press Secretary Sarah Sanders had said that no decision had been taken till then. “I know that the invitation has been extended, but I don’t believe a final decision has been made,” Sanders had said.

The Narendra Modi government has shortlisted several other heads of states, PTI reported, citing unidentified officials.

The development comes at a time when ties between New Delhi and Washington are strained, following India’s defence purchases from Russia and oil imports from Iran. New Delhi and Moscow signed a deal for S-400 air defence missile systems, despite a warning by the US that it would impose sanctions on India if the agreement went through.

In August, Trump reimposed economic sanctions against Iran and said that anyone doing business with Iran would not be doing business with the US. With the sanctions to come into force from November 4, the US expects all countries, including India, to reduce their Iranian oil imports to zero. However, India has continued to purchase oil from Tehran.

Every year, India invites world leaders to attend the January 26 parade. Modi had invited Trump for a bilateral visit to India during their talks in Washington in June 2017, PTI reported. If Trump had accepted the invitation, he would have been the second US president to attend the Republic Day celebrations as the chief guest. In January 2015, then US President Barack Obama had attended the celebrations.

Former French Presidents Nicolas Sarkozy and Francois Hollande, Russian President Vladimir Putin and Japanese Prime Minister Shinzo Abe are among other heads of states who have attended the Republic Day celebrations in India.