US President Donald Trump said he has signed letters to 12 of the country’s trading partners about the rates of tariffs that will be imposed on their products exported to the US, which will be sent on Monday.

Speaking to reporters from the presidential aircraft, Trump declined to say which countries these letters are addressed to, explaining that he will announce it on Monday.

“I have signed some letters and they will be sent on Monday, probably a dozen,” he said. “It’s easier to send a letter that says: ‘Listen we know we have a deficit or in some cases a surplus, but not in many. Here’s what you have to pay to do business with the US,'” he clarified.

“Different amounts, different tariffs,” he added. “We did it with UK and it was very good for both sides. We did it with China and I think it’s very good for both sides,” Trump explained.

The US president has set July 9 as a deadline for Washington and its partners to reach agreements regarding their trade. Otherwise, it has threatened to significantly increase tariffs on products imported into the US.

The amount of these tariffs varies on a case-by-case basis and can range from 10% to 20% or even as high as 60% to 70% and, as Trump has explained, countries will start paying them on August 1.

In early April, the US president caused a shock by announcing a drastic increase in tariffs on most imported goods: additional tariffs of 10%, with the rate going up to 50% for countries that export more to the US than they import US goods.

More than the amount of goods that more than US imports from the U.S. goes to more U.S. manufacturers than US imports.

Trump then suspended the implementation of these tariffs, paving the way for negotiations with each of the partners. U.S. officials have said a number of trade deals could be announced in the coming days.

So far, the Trump administration has only announced deals with Britain and Vietnam, while the US and China have agreed to temporarily reduce tariffs imposed by one country on the other.