The S&P 500 and the Dow Jones Industrial Average slumped on Monday as the U.S. tariffs signed into law last week by President Donald Trump weighed on industrials, though gains in tech stocks boosted the Nasdaq.

Shares of companies such as Boeing Co (BA.N), down 2.9 per cent, and Caterpillar Inc (CAT.N), down 2.4 per cent, have been under pressure as Trump's protectionist stance on steel and aluminum imports could increase costs and hamper sales abroad. Boeing and Caterpillar were the biggest decliners on the Dow.

Trump last week softened his stance on tariffs by exempting Canada and Mexico, and negotiations were ongoing as the European Union and Japan also seek exemptions.

"The big multinational, industrial companies of the world are all taking a hit on the concern that they will be the targets of reprisal sanctions," said Robert Phipps, a director at Per Stirling Capital Management in Austin.

Concerns about possible fallout from the tariffs largely supplanted optimism, based upon the modest wage growth numbers from Friday's employment report, that the Federal Reserve would stick to its projected three interest-rate increases in 2018.

Still, those numbers indicate a positive outlook for stocks despite today's losses, said Anwiti Bahuguna, a senior portfolio manager at Columbia Threadneedle in Boston.

"We've seen stable, modest wage growth, nothing that should be considered harmful for equity markets," she said.

"Growth stocks are doing well. It's pretty much a continuation of last year's rally, whereas the Dow has all sorts of other companies that may not be growth-oriented."

The Dow Jones Industrial Average fell 157.13 points, or 0.62 per cent, to 25,178.61, the S&P 500 lost 3.55 points, or 0.13 per cent, to 2,783.02 and the Nasdaq Composite added 27.52 points, or 0.36 per cent, to 7,588.33.

Even with the session's losses, the S&P 500 is just 3.1 per cent below record highs hit on Jan. 26, while the Nasdaq has recovered its losses from last month's sell-off.

The tech-heavy Nasdaq was lifted in part by further signs of official disapproval of Broadcom Ltd's US$117 billion bid for U.S. graphics chipmaker Qualcomm Inc.

The U.S. Treasury said in a letter to Singapore-based Broadcom that it had confirmed national security concerns about the bid and that the company had not given sufficient notice of its plans to redomicile in the United States.

Broadcom (AVGO.O) gained 3.6 per cent while shares in Qualcomm were flat.

Shares of Micron Technology (MU.O) rose 8.8 per cent to US$59.37 after analysts at Nomura raised their target for the stock to US$100.

Oclaro (OCLR.O) jumped 27.5 per cent after laser and optical fiber specialist Lumentum Holdings (LITE.O) said it would buy the optical components producer for US$1.7 billion. Lumentum's shares rose 4.4 per cent.

Advancing issues outnumbered declining ones on the NYSE by a 1.22-to-1 ratio; on Nasdaq, a 1.45-to-1 ratio favored advancers.

The S&P 500 posted 61 new 52-week highs and no new lows; the Nasdaq Composite recorded 211 new highs and 24 new lows.

Volume on U.S. exchanges was 6.52 billion shares, compared to the 7.2 billion average for the full session over the last 20 trading days.

CANADIAN STOCKS

Canada's main stock index closed slightly higher on Monday as gold producers overcame earlier declines and helped offset energy shares that were dragged lower by the price of oil.

The Toronto Stock Exchange's S&P/TSX composite index ended up 26.98 points, or 0.17 per cent, at 15,604.79.

The healthcare sector also helped support the market, rising 2.3 per cent. Cannabis producer Canopy Growth (WEED.TO) was among the most actively traded shares, jumping 5.0 per cent to $32.49.

Barrick Gold (ABX.TO) was among the biggest gains on the index, up 3.0 per cent at $15.59 after RBC raised its rating on the stock to "outperform." The gold subsector as a whole rose 1.1 per cent.

But losses in the energy sector kept a cap on Toronto markets as the group slipped 0.4 per cent. Canadian Natural Resources (CNQ.TO) fell 0.7 per cent to $38.63.

U.S. crude prices settled down 68 cents at US$61.36 a barrel on expectations that U.S. output will rise this year.

Shares of Bombardier Inc (BBDb.TO) fell 1.1 per cent to $3.71 after one of its Q400 planes crashed in Nepal.

The TSX posted six new 52-week highs and three new lows. Volume on the TSX index was 152.23 million shares.