• Expects US-India tariff negotiations to be relatively smooth

• Says growth in US manufacturing should benefit wider economy

• Says modifications could follow initial announcements

MUMBAI, March 12 (Reuters) - U.S. President Donald Trump's tariffs can boost manufacturing activity in the United States, the world's largest economy, Blackstone Chief Executive Stephen Schwarzman said on Wednesday.

Trump's focus on tariffs since taking office in January has shaken investors, consumers and business confidence and economists have voiced concerns of a U.S. recession that could drag down the global economy.

Schwarzman, a long-time Trump donor, speaking to reporters in Mumbai at an event to mark Blackstone's 20th anniversary in India, said he expected India-U.S. tariff negotiations to be smoother than those with other countries following a meeting between Prime Minister Narendra Modi and Trump last month.

Asked about impact of U.S. tariffs on the geopolitical order, he said said the impact would "at the end of the day" lead to a significant increase in manufacturing activity in the United States.

"Given the size of the U.S., that tends to be a good thing for the world," Schwarzman said.

"You don't know how this is all going to work out, and how initial announcements could result in actual modifications," he added, although he did not go into detail about which sectors could benefit and how tariffs would be a boost.

Trump has imposed a 25% tariff on imports of steel and aluminum into the U.S. and is planning further measures.

Blackstone meanwhile plans to double its assets under management in India in the next few years from more than $50 billion currently, Amit Dixit, head of Asia private equity at Blackstone, said on the sidelines of Wednesday's event.

The U.S investment firm counts India among its biggest markets, and is also one of the country's largest owners of office buildings, shopping malls and logistics parks.

It has built one of the three most extensive hospital chains in the country and has invested in IT services and electric vehicle components companies.

The U.S-based firm, with around $60 billion of infrastructure assets globally, is also working on investments in Indian digital infrastructure, including data centers, as well as in telecom towers, renewable energy, airports and ports, Dixit said.