The May 1 deadline for steel and aluminum tariff exemptions for U.S. allies is likely to be extended, according to sources who have been in discussions with the Trump administration.

The extensions may vary in length for each country, based on the progress made in talks on this and other trade issues. For instance, Canada and Mexico would be granted an extension because they have made progress on steel and aluminum issues in NAFTA talks, which resume late next week. It's unclear where talks with Brazil, Australia and Argentina stand.

South Korea's exemption from tariffs is permanent because it agreed to quotas as part of a new trade deal. Administration officials have asked other countries what level of quotas they would agree to.

One person briefed by the administration told CNBC: "Quotas are an active part of the discussion with every country on the exemption list."

U.S. Trade Representative Robert Lighthizer is leading the process for country exemptions, except for the European Union, which Commerce Secretary Wilbur Ross is leading. The Department of Commerce is also spearheading to process for product exemptions. The National Security Council is overseeing the entire process.

The May 1 deadline on the tariff exemptions was set in a presidential memorandum. An extension would be granted in that same way. The final decision on granting an extension will be up to President Donald Trump.

The USTR declined to comment. The White House, the Commerce Department and the National Security Council did not respond to requests for comment before publication.