It said that the tax cuts in the US will boost business investment and could add as much as 0.75 percentage point to growth this year and next in the world's largest economy.
A seagull flies by as cargo ships and an offshore supply vessel lie at anchor at sunrise off Sousse, Tunisia February 14, 2018. But it also warned that the risk of trade wars could derail expansion.
The OECD's latest Interim Economic Outlook has revised South Africa's growth rate expectations for 2018 and 2019 upward, on the back of positive sentiment around the economy and changes to the political landscape.
The higher forecast was in part due to expectations that USA tax cuts would boost economic growth there, it said.
"Growth is steady or improving in most G20 countries and the expansion is continuing", the group said.
U.S. President Donald Trump last week formally signed proclamations to impose a 25-percent tariff on imported steel and a 10-percent tariff on aluminum, causing mounting dissent among business groups and trading partners around the world.
"This could obviously threaten the recovery".
The OECD forecast the USA economy would grow 2.9 percent this year and 2.8 percent in 2019, with tax cuts adding 0.5-0.75 percentage points to the outlook in both years.
Container ships are seen at a loading terminal at the Elbe river in the harbour in Hamburg, Germany, February 6, 2017. That was higher from a November forecast of 1.2 percent due to the broader global improvement.
On Britain, the OECD struck a particularly cautious note, pencilling in growth of only 1.3 per cent this year.
Growth in France is expected to hit an 11-year high of 2.2 per cent this year before easing to 1.9 per cent in 2019. Previously, the OECD had forecast growth of 2.1 percent and 1.9 percent respectively.
Robust exports to Asia and the effect of a supplementary budget for fiscal 2017 through March will help support Japan's economic growth, the OECD said as it lifted its forecasts for the world's third biggest economy also for both years.
The body's Interim Economic Outlook - released as Chancellor Philip Hammond was preparing to paint a hopeful picture of Britain's prospects in his spring statement - nudges predicted United Kingdom growth for 2018 up by a tenth of a percentage point to 1.3%.