By PAUL HANDLEY WASHINGTON – The US crackdown on Huawei has made the Chinese telecommunications giant the flashpoint in a monumental economic and technological showdown between the two superpowers that is testing allies of both. One day after the US moved to block Huawei from the US market and banned the export of US technology and materials to the company, China warned Washington Thursday against further harming trade ties. At the same time, Beijing formally arrested two Canadians who have been detained for months on national security grounds, a move widely seen as retaliation for Ottawa's arrest of a Huawei executive last year at Washington's behest. In Britain, a heated debate continued over the government's reported decision to allow some Huawei technology in its coming 5G mobile network, a decision that has miffed Washington and led to the May 1 firing of defense secretary Gavin Williamson. And the spat over Huawei added to the uncertainty over negotiations between Washington and Beijing to end a bruising trade war, after the two sides exchanged fire with tariff hikes in recent days. ''The US's bullying and maximum pressure tactics have caused the China-US economic and trade talks to suffer a serious setback,'' Chinese Commerce Ministry spokesman Gao Feng said. ''China does not fear any pressure, and has the confidence, resolution and ability to respond to any risk and challenge,'' he added. The tough talk has hit global financial markets and stirred concerns in other capitals of dangerous fallout. ''I think launching now a technological war or a trade war vis-a-vis any other country is not appropriate,'' French President Emmanuel Macron warned Thursday. ''First, it is not the best way to defend your national security – we don't need it. Second, it is not the best way to develop your own ecosystem and have a world of cooperation and decrease tensions,'' he said. The Huawei confrontation has been building for years, as the world's largest company has raced to a huge advance on rivals in developing next-generation 5G mobile technology. The US believes Huawei is backed by the Chinese military and that its equipment could provide Beijing's intelligence a backdoor into the communications networks of rival countries. For that reason, Washington has pushed its closest allies to reject Huawei technology, a significant challenge given the few alternatives for 5G equipment. On Wednesday, President Donald Trump declared a ''national emergency'' empowering him to blacklist companies seen as ''an unacceptable risk to the national security of the United States'' – a move clearly aimed at Huawei.