President Donald Trump criticized former Secretary of State John Kerry on Monday in response to a report detailing his lobbying efforts to save the Iran deal

“The United States does not need John Kerry’s possibly illegal Shadow Diplomacy on the very badly negotiated Iran Deal,” Trump wrote on Twitter. “He was the one that created this MESS in the first place!”

Trump commented Monday after the Boston Globe revealed that the former Secretary of State was secretly speaking with Iranian Foreign Minister Javad Zarif about ways to preserve the deal.

Kerry also discussed the deal with top political officials from Germany, the European Union, and France.

The United States does not need John Kerry’s possibly illegal Shadow Diplomacy on the very badly negotiated Iran Deal. He was the one that created this MESS in the first place! — Donald J. Trump (@realDonaldTrump) May 7, 2018

Trump also mocked Kerry as “not the best negotiator” during his speech to the National Rifle Association conference.

“He never walked away from the table except to be in that bicycle race where he fell and broke his leg,” Trump said mockingly.

Publicly, Kerry has commented on Twitter about the deal, insisting that his signature foreign policy accomplishment under former President Barack Obama’s administration was “working.”

Every detail PM Netanyahu presented yesterday was every reason the world came together to apply years of sanctions and negotiate the Iran nuclear agreement – because the threat was real and had to be stopped. It's working! That’s why Israeli security experts are speaking out. 1/4 — John Kerry (@JohnKerry) May 1, 2018

Kerry is also working on a new book which will be published on September 4.