US President Donald Trump on Saturday said major US trading partners Mexico and the European Union would face a 30 percent tariff starting next month, ramping up pressure for deals in his trade wars.

Both sets of duties would take effect August 1, Trump said in separate letters posted to his Truth Social platform, citing Mexico's role in illicit drugs flowing into the United States and a trade imbalance with the EU.

The duties are higher than the 25 percent levy Trump imposed on Mexican goods earlier this year, although products entering the United States under the US-Mexico-Canada Agreement are exempted.

Canada earlier received a similar letter setting out 35 percent tariffs on its goods.

The EU tariff is also markedly steeper than the 20 percent levy Trump unveiled in April, as negotiations with the bloc continue.

The EU, alongside dozens of other economies, had been set to see its US tariff level increase from a baseline of 10 percent on Wednesday, but Trump pushed back the deadline to August 1 just days before the elevated rates were due to take effect.

Since the start of the week, Trump has sent out letters to more than 20 countries with updated tariffs for each. (AFP)