A major global stock index rose slightly yesterday after three straight days of strong gains as investors braced for news on the American trade relations with Canada and China.

Talks to renew Nafta, the North American Free Trade Agreement hinge on Canada after Monday’s deal between the other parties to that pact, the US and Mexico.

Investors are also nervous ahead of a deadline for the next round of China-US tariffs next week. MSCI’s world equity index, which tracks shares in 47 countries, ticked up 0.2 per cent. The index closed higher on Tuesday but off the 5 1/2 month high hit soon after Mexico and the United States struck their deal.

The Dow Jones rose 22.18 points to 26,086.2, the S&P 500 gained 10.99 points to 2,908.51 and the Nasdaq Composite added 55.61 points to 8,085.65.

“The market is quite right to say after the knee-jerk reaction higher in the Mexican peso and equities, a) there was remarkably little detail and b) what is the state of Canada?” said Aberdeen Standard Investments head of global strategy Andrew Milligan.

US President Donald Trump threatened to proceed with Mexico alone and levy tariffs on Canada if it does not come on board with revised terms. But a trade deal might struggle to win approval from Congress unless Canada comes on board. “The final decisions are unlikely until 2019 at the earliest,” Goldman Sachs analysts wrote in a note to clients, saying Democrats might gain control of the majority in Congress by then, which could make agreement more difficult.

The dollar, which has been a safe haven from trade concerns, turned negative after earlier gains. An index of the US currency against several trading partners fell 0.08 per cent. The Mexican peso lost 0.11 per cent versus the US dollar, while the Canadian dollar ticked down 0.09 per cent versus the greenback.

On another front of the trade conflicts, a deadline for public comment on Trump's increased tariffs on $200 billion of Chinese goods was less than a week away on September 5. The White House has said it wants to settle Nafta before negotiating with China.

“There’s a big debate taking place among investors: is Trump hoping to reach agreement with all the big players to demonstrate what a successful negotiator he is, or is he trying to make sure he’s got agreement with Nafta and the EU and can turn all the firepower on China?” said Mr Milligan.

Emerging market stocks under pressure from trade concerns and a stronger dollar this year lost 0.10 per cent yesterday, while an index of their currencies fell 0.37 per cent in dollar terms.