U.S. stocks closed higher on Monday, with the biggest boosts from technology and healthcare sectors as investors were optimistic about earnings season and appeared less worried about U.S.-led missile attacks in Syria.

The weekend's air strikes marked the biggest intervention yet by Western countries against Syrian President Bashar al-Assad and his ally Russia, which is facing further economic sanctions over its role in the conflict.

Stocks had ended lower on Friday on worries about Syria. But investors seemed less anxious about he potential for retaliation from Russia, an Assad ally, since there was none at the weekend.

"Geopolitical conditions calmed," said Tim Ghriskey, Chief Investment Strategist at Inverness Counsel in New York. "There's a lot of anticipation about very strong earnings growth in the quarter. That may be attracting traders and even longer-term investors back into the market."

Netflix shares gained around 7 percent after the market closed following its quarterly report. Its subscriber growth beat analyst expectations. It had ended the regular session down 1.2 percent.

S&P 500 companies are expected to report an 18.6 per cent jump in first-quarter profit, on average, the biggest rise in seven years, according to Thomson Reuters data.

The Dow Jones Industrial Average rose 212.9 points, or 0.87 per cent, to 24,573.04, the S&P 500 gained 21.54 points, or 0.81 per cent, to 2,677.84 and the Nasdaq Composite added 49.64 points, or 0.7 per cent, to 7,156.29.

The S&P 500's technology sector was the biggest boost to the benchmark on a weighted basis, with a 0.7-percent increase, followed by the healthcare index which rose 0.8 percent.

UnitedHealth provided the second-biggest boost to the S&P from a single stock a day ahead of its earnings report with a 2.7 per cent gain. Microsoft Corp (MSFT.O) was the biggest positive contributor with a 1.2 per cent gain, on a weighted basis.

Merck (MRK.N) rose 2.6 per cent after it presented positive data on its cancer drug Keytruda, also boosting the S&P healthcare index.

Shares of optical components makers, including those of Acacia Communications and Oclaro, took a beating after Reuters reported that the U.S. government was banning American companies from selling components to Chinese telecom equipment maker ZTE Corp. Acacia slumped almost 36 per cent, compared with a 15.2-per cent drop for Oclaro.

JB Hunt Transport Services jumped 6.2 per cent after the trucking company's profit topped estimates.

Bank of America (BAC.N) rose 0.44 per cent after a bigger-than-expected increase in quarterly profit.

Advancing issues outnumbered declining ones on the NYSE by a 2.70-to-1 ratio; on Nasdaq, a 1.82-to-1 ratio favored advancers.

The S&P 500 posted 11 new 52-week highs and no new lows; the Nasdaq Composite recorded 68 new highs and 36 new lows.

On U.S. exchanges about 5.74 billion shares changed hands, in the lowest volume session so far this year. Monday's trading compared with the 7.03 billion average for the last 20 sessions.

CANADIAN STOCKS

Canada's main stock index rose on Monday, led by industrial and financial shares, as fears waned of an escalating conflict in Syria following the weekend's U.S.-led air strikes.

The Toronto Stock Exchange's S&P/TSX composite index closed up 26.41 points, or 0.17 per cent, at 15,300.38. It was the third straight day that the index has ended modestly higher.

Gains for the TSX came as investors on Wall Street turned their focus to earnings season and appeared less worried about the Middle East.

Industrials rose 0.8 pe rcent, including gains for railroad shares. The financials group, which accounts for more than one-third of the weight of the TSX, gained 0.2 per cent.

Eight of the index's 10 main groups rose.

The energy group fell 1.7 per cent as oil prices declined.

The largest percentage gainer on the TSX was Aphria Inc (APH.TO), which rose 7.4 per cent, while the largest decliner was Enerflex Ltd (EFX.TO), down 6.9 per cent.

The TSX posted four new 52-week highs and four new lows.