Canadian Prime Minister Justin Trudeau and US President Donald Trump have discussed the current expulsion of Russian diplomats and the North American Free Trade Agreement (Nafta) during a phone call, the Canadian Prime Minister's Office said on Tuesday.In their conversation on Monday, the two leaders discussed measures taken by Canada and the US to support Britain, their common ally, against Russia in response to the "egregious nerve agent attack in Salisbury", Xinhua news agency cited a statement as saying.Trudeau also underscored his country's commitment to conclude a modern, mutually beneficial Nafta as soon as possible and mentioned the "strong measures" Canada was taking to address unfair trade in steel and aluminium.On the diplomats' expulsion, Moscow vowed to retaliate in kind after 25 Western nations decided to expel Russian diplomats over the country's alleged involvement in the poisoning of a former Russian spy and his daughter by using a chemical weapon on March 4 in Britain. The Russian government fiercely denied any role in the case.