(Repeats story with no changes to text) By David Lawder WASHINGTON, May 5 (Reuters) – The United States and Britain launch trade negotiations by videoconference on Tuesday following the UK’s exit from the European Union, as both allies struggle with the effects of the coronavirus pandemic and aim to shore up domestic supply chains. The talks will be Washington’s first major new trade negotiation in 2020, and take place at the same time as London works out trade terms with the EU, with a year-end deadline. U.S. Trade Representative Robert Lighthizer has said little publicly about the UK trade talks since publishing a sweeping set of objectives more than a year ago that sought full access for U.S. agriculture products and reduced tariffs for U.S. manufactured goods. The Trump administration is looking to shift supply chains back to the United States and away from China, where the novel coronavirus originated, and is pushing a “Buy American” campaign for medical and other supplies. Agriculture is expected to be among the thorniest issues in the talks, given the strong British opposition to U.S. genetically modified crops and antibacterial treatments for poultry. Prime Minister Boris Johnson has vowed to drive a “hard bargain”…