British Prime Minister David Cameron, visiting Ottawa on Thursday, joined his Canadian counterpart Stephen Harper in calling for “decisive” action on curbing the European debt crisis. Cameron was in Ottawa for a brief bilateral visit, meeting in private with Harper before addressing the House of Commons. In his speech, he emphasized that he would never support Britain’s entry into the eurozone—the area made up of European countries using the euro—but that his country has a vital interest in that region’s economic stability. “The problems in the eurozone are now so big that they have begun to threaten the stability of the world economy,” he said. Both Harper and Cameron joined other world leaders in signing an open letter to French President Nicolas Sarkozy, who will chair the upcoming G20 meeting in Cannes. The letter expresses the perceived urgency in reinstating investor confidence in global markets and curbing public debt in many countries.