(Recasts, adds international market context)

BUENOS AIRES, April 2 (Reuters) - Bad weather and coronavirus are walloping Argentina’s key soy export industry, with a grains exchange cutting its harvest estimate on Thursday as a long line of cargo ships dropped anchor in the Parana River, delayed by health inspections.

Argentina is the world’s No. 3 corn and soybean exporter, as well as its top supplier of soymeal livestock feed.

Disruptions in shipments from Argentina can throw off world trade flows and importers - particularly pork, poultry and beef producers in Europe and Southeast Asia - look to rival soymeal exporters Brazil and the United States to fill the supply gap.

The country’s soy crop is expected at 49.5 million tonnes, the Buenos Aires Grains Exchange said, citing bad weather and lower-than-expected yields as the reason for chopping its earlier 52-million-tonne forecast.

The lower estimate hits farmers just as transportation problems stemming from the coronavirus pandemic cause logistics bottlenecks that have hurt exports. Some 28 ships have been delayed as they tried to enter Parana River export hubs, according to local maritime agency NABSA.

Port administrators say day-long health inspections have bogged down river traffic while some truckers’ unions and municipal governments object to using the roads to transport commodities in Argentina on the grounds that it could help spread the virus while the rest of the country is on lockdown.

Argentina has lost 34 lives to the virus so far with, 1,133 cases confirmed, according to government data.

The pandemic hits as the government struggles to avoid default on more than $100 billion in debt - including bonds held by private investors and International Monetary Fund loans - that it calls unsustainable. Agriculture is the country’s biggest source of much needed export dollars.

The lower-than-expected soy yields stem from the extreme dryness that blighted the Pampas farm belt in February and early March. Since then, growers have had to contend with unusually rainy conditions that have made some roads impassable and soils too wet to allow heavy harvesting combines to enter fields.

“Interrupted by rains in large sectors of the agricultural belt, the soybean harvest advanced 3.5 percentage points over the last seven days to 8.1% of planted area,” the exchange said in the report.

The exchange maintained its 50-million-tonne corn harvest forecast unchanged. Some 22.2% of the 2019/20 corn crop has been harvested so far, the report said. (Reporting by Hugh Bronstein and Maximilian Heath Editing by Chris Reese, Marguerita Choy, Richard Chang and Sonya Hepinstall)