WASHINGTON/BEIJING, August 2, 2018 (News Wires) -- US President Donald Trump sought to ratchet up pressure on China for trade concessions by proposing a higher 25 per cent tariff on $200 billion worth of Chinese imports, his administration said on Wednesday. US Trade Representative Robert Lighthizer said Trump directed the increase from a previously proposed 10 per cent duty because China has refused to meet US demands and has imposed retaliatory tariffs on US goods. "The increase in the possible rate of the additional duty is intended to provide the administration with additional options to encourage China to change its harmful policies and behaviour and adopt policies that will lead to fairer markets and prosperity for all of our citizens," Lighthizer said in a statement. There have been no formal talks between Washington and Beijing for weeks over Trump's demands that China make undamental changes to its policies on intellectual property protection, technology transfers and subsidies for high technology industries. Derek Scissors, a China scholar at the American Enterprise Institute in Washington, said a 25 percent tariff rate is more likely to shut out Chinese products and shift American supply chains to other countries, as a 10 per cent duty could be offset by government subsidies and weakness in China's yuan currency. "If we're going to use tariffs, this gives us more flexibility and it's a more meaningful threat," he said, adding that Trump's pressure strategy will not work if he does not resolve trade disputes with US allies such as the European Union, Mexico and Canada. But the move drew swift condemnation from US business lobby groups worried that tit-for-tat tariffs would start to hamper economic growth. "Escalating tariffs against China is the wrong approach to address legitimate concerns US businesses have with China's harmful practices," said Myron Brilliant, head of international affairs for the US Chamber of Commerce. "Each tariff escalation leads to further retaliatory action from China – ultimately inflicting even more harm on American businesses, workers, farmers, ranchers, and consumers." China called the move "blackmail," and warned it would respond in kind.