(Bloomberg) -- Supply Lines is a daily newsletter that tracks trade and supply chains disrupted by the pandemic. Sign up here.

South Korea’s early trade data show exports are set to slow in September, adding to signs that an outbreak of the delta variant of coronavirus is weighing on a global recovery. 

Exports rose 22.9% in the first 20 days of September from a year earlier, the customs office reported Thursday. Average daily shipments gained 31.3% in the period, which had one less business day than last year.

Korea’s trade data is an early indicator of global economic activity as its manufacturers are positioned widely across supply chains. Exports have rallied this year as the world economy gradually recovered from the pandemic, but the fast-spreading delta strain has clouded the outlook by causing shutdowns in factories and ports that are crucial in keeping goods flowing across borders.

Manufacturing activity in China -- the largest trade partner for Korea and many others -- slowed in the latest report, fueling concerns about the strength of the global recovery.

©2021 Bloomberg L.P.