Delta Air Lines on Tuesday postponed indefinitely flights to Kenya after failing to get US government approval to fly to east Africa's biggest economy.

The inaugural Delta flight was due to arrive in Kenya's capital Nairobi on Wednesday afternoon for a ceremony to be attended by Prime Minister Raila Odinga, the US envoy to Kenya, government ministers and Delta officials.

"The start of Delta Air Lines new direct flight from Nairobi to Atlanta has been postponed indefinitely following a decision by the US Department of Homeland Security that the agency required more time to review these flights," a local public relations firm acting for Delta said in a statement.

Delta said last year it was adding 15 new international routes to Asia, Africa, Europe and the Middle East to protect itself from a slowing US economy.

The Kenyan government said it hoped Delta would soon join other international airlines, such as British Airways, which already fly direct to Nairobi.