By Aditya Kalra, Abhijith Ganapavaram and Munsif Vengattil

NEW DELHI (Reuters) - Tech giant Apple (AAPL) chartered cargo flights to ferry 600 tons of iPhones, or as many as 1.5 million, to the United States from India, after it stepped up production there in an effort to beat President Donald Trump's tariffs, sources told Reuters.

The details of the push provide an insight into the U.S. smartphone company's private strategy to navigate around the Trump tariffs and build up inventory of its popular iPhones in the United States, one of its biggest markets.

Analysts have warned that U.S. prices of iPhones could surge, given Apple's high reliance on imports from China, the main manufacturing hub of the devices, which is subject to Trump's highest tariff rate of 125%.

That figure is far in excess of the tariff of 26% on imports from India, but which is now on hold after Trump called a 90-day pause this week that excludes China.

Apple "wanted to beat the tariff," said one of the sources familiar with the planning.

The company lobbied Indian airport authorities to cut to six hours the time needed to clear customs at the Chennai airport in the southern state of Tamil Nadu, down from 30 hours, the source added.