The Indian rupee weakened past 87 to the U.S. dollar for the first time ever on Monday in the wake of a slump in Asian currencies and equities after U.S. President Donald Trump's tariff threats became a reality.

The rupee breached the key 87 per dollar mark on Monday as the dollar strengthened after US President Trump slapped tariffs on Canada, Mexico and China. The dollar index surged by 1.35 per cent to 109.83. It measures the strength of the greenback against a basket of six major currencies.

The dollar index was up 0.3% at 109.8, while Asian currencies weakened, with the offshore Chinese yuan down 0.5% at 7.35 per US dollar.

The Indian rupee weakened past 87 per U.S. dollar for the first time on Monday, as Asian currencies slumped after U.S. President Donald Trump imposed tariffs on the country's largest trading partners,