For South Africa, the OECD has revised the expected GDP growth rate upward to 1.9% in 2018, and 2.1% in 2019 - higher than the growth rate now targeted by National Treasury.
Contributing to the positive outlook were tax reductions and increased spending in the world's largest economy, the United States, and fiscal stimulus in Europe's economic powerhouse Germany, according to the OECD.
The OECD forecast the United States economy would grow 2.9 per cent this year and 2.8 per cent in 2019, with tax cuts adding 0.5-0.75 percentage points to the outlook in both years.
Canada's growth is expected to slow to two per cent next year, but that's also better than previous expectations, which were for 1.9 per cent as of three months ago.
It said rebounding business investment was the core reason for the expected acceleration in global growth - with trade rising 5% this year. While stronger growth is being called for, it does warn of risks to growth and to jobs if trade tension escalates further.
"Safeguarding the rules-based worldwide trading system will help to support growth and jobs", it said.
Last week, President Trump signed controversial orders imposing heavy tariffs on steel and aluminium.
The German rise will be slightly higher than that of the euro area as a whole, with a forecast increase of up to 2.3% in 2018 and 2.1% in 2019 (two tenths more in both cases).
He said: "Investment is coming back, and so this is very good news for good new for jobs and growth across the economies".
"Governments should avoid escalation and rely on global solutions to resolve excess capacity in the global steel industry", it said.
The OECD stressed that the world economy would continue to strengthen in 2018 and 2019.
As growth recovers, monetary policy across the world is gradually returning to more normal levels after years of highly expansionary central bank action.
The eurozone economy will likely see a robust and broad-based expansion, with growth in gross domestic product estimated at 2.3 percent this year and 2.1 percent next year.
The UK economy will grow slower this year than any other major advanced country in 2018.
With Britain due to leave the European Union next year, its economic growth was seen easing to 1.1 per cent in 2019, unchanged from the OECD's November estimate.