There have been differences between India, US over S-400 deal with Russia. (File)

Highlights Trump was "honored" by PM Modi's invitation: White House spokesperson

India had invited Trump earlier this year

India, US have differences over S-400 Russia deal, oil imports from Iran

The White House has officially commented for the first time on President Donald Trump's decision to turn down Prime Minister Narendra Modi's invite to India's Republic Day as chief guest.

A White House spokesperson told NDTV that President Trump couldn't accept the invite because of scheduling constraints.

"President Trump was honored by Prime Minister Modi's invitation for him to be Chief Guest of India's Republic Day on January 26, 2019 but is unable to participate due to scheduling constraints," the spokesperson said.

"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 U.S.-India strategic partnership. The President very much looks forward to meeting Prime Minister Modi again at the earliest opportunity."

India invited President Trump earlier this year and had he accepted, he would have been the second US president to come for Republic Day. President Barack Obama visited India twice and was chief guest at the Republic Day celebrations on his second visit in 2015, a year after PM Modi came to power.

President Trump's decision comes at a time there have been differences between the two countries over India's defence purchases from Russia and oil imports from Iran.

India's insistence on buying oil from Iran despite US sanctions on the oil-producing nation did not go well with the Trump administration.

The Modi government also decided, despite the threat of US action, to buy the Russian S-400 long-range missile system, which America considers is within the scope of the Countering America's Adversaries Through Sanctions Act.

The S-400 missile system is arguably the world's deadliest surface-to-air missile and the US believes the weapon can bring imbalance on the battlefield if it falls in wrong hands. Russia's deployment of the missile system in Syria is seen as a threat to the West.