US benchmark equity indexes lost more ground after President Donald Trump reiterated that the proposed tariffs on Mexico and Canada will go ahead as planned.

The Nasdaq Composite declined 2.6% to 18,350.2 on Monday, while the S&P 500 fell 1.8% to 5,849.7. The Dow Jones Industrial Average lost 1.5% to 43,191.2. Among sectors, technology and energy saw the biggest declines. Real estate led the gainers.

Stock markets were already trading lower intraday, but the selloff intensified after Trump said the US is set to impose 25% tariffs on the Mexican and Canadian imports Tuesday, as originally planned, CNBC reported. "They're all set. They go into effect tomorrow," Trump reportedly said.

In economic news, two surveys painted a mixed picture of the US manufacturing sector in February, with the Institute for Supply Management's data pointing to a slower expansion rate sequentially and S&P Global (SPGI) indicating the best growth rate since June 2022.

The ISM survey showed that price pressures are likely "stirring again" in the production pipeline, BMO Capital Markets said. "This is not what the (Federal Reserve) wants to see -- especially at a time when firms could soon potentially be dealing with the impact of major tariffs."

Policymakers have "more work to do" to achieve price stability, with inflation still above their 2% target, St. Louis Fed President Alberto Musalem said. "I believe a patient policy approach now will help us as we seek maximum employment, price stability and a durable economic expansion."

US Treasury yields slid Monday, with the 10-year dropping 6.8 basis points to 4.161% and the two-year rate falling 3.5 basis points to 3.96%.

In company news, Nvidia shares slid 8.7%, the steepest decline on the Dow and among the worst on the S&P 500. Servers linked to a fraud case in Singapore may have included Nvidia chips and were supplied by Dell Technologies (DELL) and Super Micro Computer (SMCI) to local companies before being delivered to Malaysia, news outlets reported, citing Singapore's Home Affairs and Law Minister K. Shanmugam.

Dell shares declined 7%, while Super Micro's tumbled 13%, the worst S&P 500 performer.

Verizon (VZ) was the top gainer on the Dow, up 1.8%. Lockheed Martin (LMT) said Sunday it is partnering with Nokia (NOK) and Verizon to incorporate Nokia's 5G technology into its 5G.MIL Hybrid Base Station, which connects commercially available 5G with military communication systems.

Lockheed Martin rose 1.1% Monday.

S&P 500 companies' latest quarterly results showed an acceleration in growth rates of both earnings and sales, compared with financials reported until a week ago, Oppenheimer Asset Management said Monday.

West Texas Intermediate crude oil fell 2% to $68.36 a barrel.

Gold rose 1.9% to $2,903.8 per troy ounce, while silver gained 2.4% to $32.24 per ounce.