Canada’s prime minister sought to cool expectations about reaching a trade agreement with the US in the next 10 days, saying the talks are difficult because the Trump administration keeps changing its goals.

The prospect of Canada reaching a trade deal with the United States by the Aug. 1 deadline appears uncertain, with Prime Minister Mark Carney insisting his government will only sign a new agreement if there is one worth signing.

Canada will use all the time that is available to strike a trade deal with the United States, Prime Minister Mark Carney told reporters on Tuesday, saying the talks were complex.