A key reason for US President Donald Trump's failure to galvanize international support are his undiplomatic, ill-advised behaviors, which have alienated American allies. Photo: Reuters/Joshua Roberts

President Trump plans to decertify the international nuclear agreement with Iran, sources briefed on the White House strategy said Thursday, according to a Washington Post report.

The announcement will be made in a speech next week, the people said, marking the first step in a process that could see the resumption of US sanctions against Iran.

The four sources stressed that the decision is not yet official and that the President will hold off on recommending that Congress reimpose sanctions, an action that would abrogate the agreement.