WASHINGTON, June 3 (Xinhua) -- Kevin Hassett, chairman of the White House Council of Economic Advisers (CEA), said Monday his stepping down is not related to President Donald Trump's decision to hike tariffs against Mexico.

Asked in an interview with CNBC's "Squawk Box" morning program whether Trump's announcement of the Mexico tariffs led to his departure, Hassett said, "No, I mean this is something that's been in the works for a little while."

"If you look at the history of the CEA, it's very normal for the chair to move on after two years," added the 57-year-old CEA chief, who wrote Trump a resignation letter Friday.

Hassett was sworn in on Sept. 13, 2017 as the 29th head of the CEA.

The CEA chair said that he resigned partly out of "respect for the institution," and that "there is also just wanting to go back and spend time with my family."

Hassett told Trump in the resignation letter that he looks forward to spending some more time with his family and hopes "to continue to be a resource to you from the outside."

He also said he will stay in his role until the end of June to help ensure a smooth transition at the CEA.

Noting during the CNBC interview that the longer one works in the White House, "the harder it might be to be objective," Hassett said, however, his departure and Trump's threat made Thursday to impose tariffs of 5 percent on all Mexican imports are separate issues. "I think it's appropriate that we just separate them."

Trump tweeted Sunday that Hassett "will be leaving shortly," adding that he will name a "very talented replacement" as soon as he returns from a trip to Europe, which takes him to Britain, Ireland and France.

Hassett refused to speculate on who his successor might be when pushed by one of the CNBC hosts. "The CEA is going to be fine," he said.