The U.S. president announced that he had signed letters to 12 countries outlining the tariff levels they would face on goods exported to the United States, with the “take it or leave it” offers set to be sent out on Monday. Speaking to reporters aboard Air Force One while traveling to New Jersey, he declined to name the countries involved, saying that information would be made public on Monday.

Earlier on Thursday, he had told reporters that he expected the first batch of letters to go out on Friday, a national holiday in the United States, but the date has since shifted. In a global trade dispute that has unsettled financial markets and triggered a rush among policymakers to protect their economies, he announced in April a 10% base tariff rate with additional amounts for most countries, some as high as 50%.

However, all but the 10% base rate were suspended for 90 days to allow more time for negotiations to secure deals. That suspension period ends on July 9, although early on Friday he said the tariffs could be even higher — ranging up to 70% — with most set to go into effect August 1.

“I signed some letters and they’ll go out on Monday, probably twelve,” he said, when asked about his plans on the tariff front. “Different amounts of money, different amounts of tariffs.”

Initially, he and his top aides planned to negotiate tariff rates with dozens of countries, but he has grown frustrated with that process following setbacks with major trading partners including Japan and the European Union. He briefly addressed this late on Friday, telling reporters: “The letters are better … much easier to send a letter.”

He did not address his earlier prediction that broader trade agreements might be reached before the July 9 deadline. The change in strategy reflects the difficulties in completing trade agreements covering tariffs and other barriers such as agricultural import bans, especially on an accelerated timeline. Most past trade agreements have taken years to negotiate.

So far, the only trade deals reached are with Britain, which secured a May agreement to keep a 10% tariff rate and won preferential treatment for sectors like autos and aircraft engines, and with Vietnam, cutting tariffs on many Vietnamese goods to 20% from the previously threatened 46%. Many U.S. products would be allowed duty-free entry into Vietnam.

A deal expected with India has not materialized, and EU diplomats recently said they have failed to make progress in trade talks with the administration and may now seek to extend the current situation to avoid tariff hikes.