United States Ambassador to India Kenneth Juster on Thursday said President Donald Trump is unable to participate in the Republic Day celebrations because of scheduling constraints, PTI reported.

Trump has declined India’s invitation to be the chief guest at the parade on January 26 citing a “crowded calendar”, which include the State of Union address – likely to be held between January 21 and 29. Every year, India invites world leaders to attend the January 26 parade.

“It is completely a scheduling issue,” Juster said on the sidelines of the South Asia Regional Connectivity Conference 2018 in Delhi.

On Tuesday, the US had expressed Trump’s inability to attend the Republic Day celebrations. “The president enjoys a strong personal rapport with Prime Minister Modi developed through two meetings and several phone calls and remains committed to deepening the US-India strategic partnership,” a White House spokesperson said, according to Mint. “The president very much looks forward to meeting Prime Minister Modi again at the earliest opportunity.”

On Tuesday, the Congress claimed Trump rejecting India’s invitation was a “diplomatic faux pas” and an embarrassment for the country. “The invitation should not have been sent in the first place without having an assurance, that once it reaches Washington, it will be accepted,” PTI quoted Congress leader Anand Sharma as saying.

Sharma said Modi sees foreign policies only as photo opportunities. “This government’s foreign policy is incoherent, is episodical and Prime Minister Modi must remember that engagement with major strategic partners cannot be transactional, but must have a ring of continuity, coherence and correctness.”

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.