India and the European Union have finalised a landmark trade deal that will represent a quarter of the world's economy, Indian Prime Minister Narendra Modi said on Tuesday, as the two sides seek to hedge against fickle ties with the U.S, Reuters reported. 

After nearly two decades of on-off negotiations, the deal will pave the way for India to open up its vast and guarded market, the world's largest, to free trade with the 27-nation EU, its biggest trading partner.

"Yesterday, a big agreement was signed between the European Union and India," Modi said, according to Reuters.