RICHFIELD, Ohio (REUTERS) - US President Donald Trump said on Thursday (March 29) he may hold up a trade agreement reached this week with South Korea until after a deal is reached with North Korea on denuclearisation.

“I may hold it up until after a deal is made with North Korea,” Trump said in a speech. “You know why? Because it’s a very strong card. And I want to make sure everyone is treated fairly,” he added.

Senior US officials have expressed concerns privately that Seoul is the weak link in the US-Japan-South Korean alliance and could be too quick to seal a deal with North Korea.

Trump agreed this month to accept an invitation to meet with North Korean leader Kim Jong Un. South Korean officials have said the meeting would take place by the end of May, after a North-South summit in April.

“We’re moving along very nicely with North Korea. We’ll see what happens. Certainly the rhetoric has calmed down just a little bit,” Trump told construction workers in Ohio.

The United States and South Korea earlier this week agreed to revise their six-year-old free trade agreement with a side deal to deter competitive currency devaluation by Seoul and more access for US automakers and drug makers to the South Korean market.

The deal also lifts the threat of a 25 per cent US tariff on imports of steel from South Korea in exchange for quotas that will effectively cut US imports of Korean steel by about 30 per cent. Without the agreement in place, the tariffs would take effect May 1.

Related Story Pledges of better ties and denuclearisation at Kim-Xi meeting

A statement by US Trade Minister Robert Lighthizer and South Korean Trade Minister Hyun Chong Kim described steel terms as being agreed, with the KORUS free-trade deal changes as an“agreement in principle on the general terms” while details are still being finalized.

The US Treasury and the South Korean Ministry of Strategy and Finance are finalizing the currency terms, they said.

The trade deal changes, which preserve the US-South Korean trading relationship at a critical time for Seoul, do not need Congress’ approval but are subject to a 60-day consultation period with Seoul.

A spokeswoman for the US Trade Representative’s office did not respond to a Reuters request for clarification on Trump’s comments.

State Department spokeswoman Heather Nauert told reporters that she had not heard the president’s remarks, but added: “This is not a done deal. It’s not a final agreement.”