He's currently an adviser to Federica Mogherini, the current High Representative of the European Union for Foreign Affairs.
Ustubs will be the second Latvian diplomat serving as an EU ambassador. In September Eduards Stiprais became the head of the Delegation of the European Union to Uzbekistan.
Cooperation with Canada is high on Latvia's agenda as the country is sending its troops to Latvia as part of a NATO-lead mission designed to deter an increasingly aggressive Russia following its 2014 occupation of Crimea.
Around 455 Canadian troops will arrive to Latvia in June as part of a 1,200-strong multinational battalion.