U.S. President Donald Trump said that the United States will begin sending out letters notifying tariff rates to 12 to 15 countries starting Monday.

Speaking to reporters before boarding Air Force One in New Jersey on Sunday, Trump added that more letters would be sent on Tuesday and Wednesday.

He said the U.S. has also made some deals with some countries, so there will be a mix of letters and deals.

Trump added that negotiations with most countries are expected to conclude by July 9, resulting in either a formal agreement or the issuance of a tariff letter.

Standing alongside the president, U.S. Commerce Secretary Howard Lutnick confirmed that the tariff rates will take effect on August 1 and said Trump is actively engaged in trade talks with various nations.