ZURICH/FRANKFURT, Oct 30 (Reuters) - AstraZeneca has enlisted contract manufacturer Lonza to produce a combination of two antibodies that may help prevent and treat COVID-19, part of a class of drugs the U.S. government sees as a promising way to combat the pandemic.

Switzerland's Lonza said it would manufacture the antibodies for the combination treatment, called AZD7442, at its facilities in Portsmouth, New Hampshire. Operations are expected to start in the first half of 2021.

The U.S. government this month awarded $486 million to AstraZeneca to develop and secure supplies of up to 100,000 doses of the experimental treatment.

AstraZeneca declined to disclose volumes or other terms of the Lonza contract, but a spokesman said Lonza would be part a global supply chain.

He added AstraZeneca would likely make more announcements on supplies in future, potentially involving its own sites or external partners.

AZD7442 is in Phase I clinical studies and AstraZeneca said on Oct. 9 it planned to advance it into final Phase III trials in the coming weeks.

AstraZeneca's agreement under the U.S. government's Operation Warp Speed programme is to develop a monoclonal antibody cocktail especially for high-risk people, such as those over 80 years old.

Targeted antibodies made by biotech firm Regeneron were used to treat President Donald Trump's COVID-19 infection. The company signed a $450 million U.S. government deal in July to sell doses for the treatment of around 300,000 people. (Reporting by Michael Shields in Zurich and Ludwig Burger in Frankfurt; editing by Thomas Seythal and Mark Potter)