Britain and India agreed to a trade deal on Tuesday, strengthening economic ties between two of the world’s largest economies amid President Trump’s upheaval of the global trade system.

The deal, which the British government said would increase bilateral trade by £25.5 billion ($34 billion), comes three years after the negotiations began. Intense talks between Jonathan Reynolds, Britain’s business and trade secretary, and Piyush Goyal, India’s commerce minister, took place last week to finalize the outstanding issues.

The British government said India had reduced 90 percent of tariffs on goods, and within a decade most of those would become tariff free. Duties on British whiskey and gin would be halved, to 75 percent, and eventually be lowered to 40 percent. India will also reduce its car tariffs, which exceed 100 percent, to 10 percent under a quota. Britain, in turn, reduced tariffs on clothes, footwear and food products including frozen prawns.

Last year, trade in goods and services between India and Britain, the world’s fifth and sixth largest economies, totaled £42.6 billion, according to British data.

The trade agreement comes as many countries are seeking to bolster alliances and trade flows after Mr. Trump sent shock waves through the global economy by announcing, and then pausing, high tariffs on dozens of countries. The uncertainty created by the policy whiplash is expected to dampen investment and economic growth around the world.

Officials in Britain, which squeezed out 0.1 percent economic growth in the final quarter of last year, have tried to increase investment from foreign companies and sign more trade deals. Other negotiations, including those with South Korea, are continuing.