Adds Indian foreign secretary, Lockheed Martin comments in paragraphs 6-8

By Nandita Bose and Mike Stone

WASHINGTON, Feb 13 (Reuters) - The United States will increase military sales to India starting in 2025 and will eventually provide F-35 fighter jets, U.S. President Donald Trump said on Thursday.

"We'll be increasing military sales to India by many billions of dollars. We're also paving the way to ultimately provide India with the F-35 stealth fighters," Trump told reporters.

Trump did not provide a timeline, but foreign military sales, especially for cutting-edge technology like the stealthy F-35 jet, typically take years to work through.

Addressing a joint news conference after a meeting with Indian Prime Minister Narendra Modi, Trump also said the countries had struck an agreement that includes India importing more U.S. oil and gas to shrink the trade deficit between the two countries.

Trump also said that Washington and New Delhi will be working together to confront what he called "the threat of radical Islamic terrorism."

Indian Foreign Secretary Vikram Misri told reporters later that New Delhi follows an elaborate process for foreign military purchases including seeking proposals from manufacturers and evaluating them.

"I don't think with regard to the acquisition of an advanced aviation platform by India, that process has started as yet," he said when asked about the F-35 announcement by Trump. "This is currently something that's at the stage of a proposal."

Lockheed Martin LMT.N, which makes the F-35 jet, said that any discussions about the sale of F-35 to India would take place at the government-to-government level.

Foreign military sales like those of the F-35 are considered government-to-government deals where the Pentagon acts as an intermediary between the defense contractor and a foreign government.

India has agreed to buy more than $20 billion of U.S. defense products since 2008. Last year, India agreed to buy 31 MQ-9B SeaGuardian and SkyGuardian drones after deliberations that lasted more than six years.

According to the U.S. Congressional Research Service, New Delhi is expected to spend more than $200 billion over the next decade to modernize its military.

Lockheed is producing three models of the new warplanes for the U.S. military and allies including Britain, Australia, Italy, Turkey, Norway, the Netherlands, Israel, Japan, South Korea and Belgium.

Russia has for decades been the main weapons supplier to India, the world's biggest arms importer, and its fighter jets are part of India's military fleet. But Moscow's ability in recent years to export has been hobbled by the war in Ukraine, making New Delhi look westward.

Russia has offered to make its fifth-generation stealth fighter jet Sukhoi Su-57 in India for the Indian Air Force, a Russian and an Indian official said on Tuesday, as Moscow looks to maintain strong ties with New Delhi.

(Reporting by Jarrett Renshaw, Nandita Bose, Mike Stone and David Brunnstrom; Additional reporting by YP Rajesh and Shilpa Jamkhandikar; Writing by Ismail Shakil; Editing by Jamie Freed)

((jarrett.renshaw@thomsonreuters.com; (646) 223-6193;))