Trudeau was in Halifax to speak to the annual conference of the Federation of Canadian Municipalities. This could mean that the EU will either neutralize or retaliate against the USA with European tariffs.
The trade actions have opened the U.S.to criticism that it's burning bridges at a time when Trump is seeking to rid North Korea of nuclear weapons and help stabilize the Middle East.
Trudeau said he refused to go because of the "totally unacceptable" precondition.
The Tory peer, speaking on the Today programme, urged the Government and the European Union not to embark on a "tit-for-tat" policy and instead stick "robustly to free trade".
Mr Gardiner urged the Government to "strongly respond" after US President Donald Trump signed off on a 25% levy on imported steel.
Finance Minister Bill Morneau, who chaired the Whistler meetings, said even though the group found common ground on many subjects, G7 members are now forced to do whatever they can to convince Trump to move back from the tariffs.
The EU is also planning retaliatory tariffs on USA steel and food in the coming weeks, once the cost of the U.S. tariffs becomes clear.
"President Trump has been very clear in wanting to address trade issues".
The EU took the United States to the World Trade Organization to challenge the legality of the new tariffs and the Trump administration's national-security justification. The bloc plans to impose 25 percent tariffs on around 200 American products by June 20.
Macron also proposed to start negotiations between the US, the EU, China and Japan to reshape the World Trade Organization to better regulate trade.
The 28-member bloc has "no choice" but to bring a case before the World Trade Organisation and impose duties on United States imports, Commission president Jean-Claude Juncker said, calling the tariffs "totally unacceptable".
A list of countermeasures would include tariffs on US metals and food products such as yogurt, pizza and cucumbers, as well as household products like mattresses and refrigerators. But he granted an exemption to the European Union and other US allies; that reprieve expires Friday.
The UK's Secretary of State for International Trade Liam Fox told Sky News it, too, is considering retaliatory measures and joining the EU's complaint with the WTO.
The White House released a statement from Trump on Thursday night saying of NAFTA, "Earlier today, this message was conveyed to Prime Minister Justin Trudeau of Canada: The United State (sic) will agree to a fair deal, or there will be no deal at all".
But Macron said those "who waged bilateral trade wars. saw an increase in prices and an increase in unemployment".
As its first step to challenge the US tariffs, the European Union on Friday formally filed a request for consultations at the WTO.