Stocks looked set to struggle for direction on Monday after President Donald Trump threatened to impose further tariffs on Canada, boosting the likelihood that the “sell America” trade could gather pace this week. Gold futures jumped 2.3% to $5,094 an ounce, meaning bullion passed the $5,000 level for the first time ever, and silver futures surged 7.2% to $109 an ounce. The yield on the 10-year Treasury note slipped 3 basis points to 4.21%.