SANTIAGO, March 20 (Reuters) - Codelco, the world's No. 1 copper producer, has been unable to export some metal from its massive mines due to a strike by port workers in northern Chile, the company said on Wednesday. Angamos, located roughly 65 kilometers (40.4 miles) from the city of Antofagasta, is one of several ports state miner Codelco uses to ship out its copper. "The material is being received at the port, but it is not being sent out," the company told Reuters. "There's a ship waiting to be loaded." It wasn't clear how many tonnes were involved or when shipments would resume, Codelco said. Codelco expects its copper output to reach around 1.7 million tonnes this year, boosted by the launch of its Ministro Hales mine. The miner is also facing a potential internal work stoppage. Codelco's unionized workers threatened on Friday to stage a 24-hour stoppage at all the miner's units within 30 days to demand greater job security. In the January to September period last year, 36 percent of Codelco's sales were to top metals consumer China, 22 percent to the rest of Asia, 18 percent to Europe, 12 percent to fellow South American countries ,and 11 percent to North America.