Economic growth in China and the United States could be 0.2-0.3% lower on average by 2021 and 2022 if the two countries do not row back on tit-for-tat tariffs in their dispute that has dampened the global economic outlook, the OECD said on Tuesday.

The global economy would grow by only 3.2% this year as growth in trade flows is nearly halved this year to only 2.1%, the Organisation for Economic Cooperation and Development (OECD) said in its biannual Economic Outlook.

That would be the slowest pace of global economic growth since 2016 and was down marginally from the Paris-based policy forum's last forecast in March for growth of 3.3%.

The world economy should fare slightly better next year with a growth rate of 3.4%, but only if the United States and China pull back from tariff hikes announced this month.

The OECD said growth in China and the United States could come in 0.2-0.3% lower on average by 2021 and 2022 if the two nations did not reverse course.