Testing the limits of presidential power, Donald Trump this week tightened his grip on U.S. government agencies that for years have taken pride in their independence overseeing such matters as elections, stock markets and labor unrest.

Trump's order on Tuesday was the latest show of force in a series that has removed critics from office, defunded federal programs, loosened government oversight and frozen billions of dollars in spending approved by Congress.

The order allows the White House to shift the budget and policies of the Federal Election Commission, the Securities and Exchange Commission, the National Labor Relations Board and other agencies whose day-to-day activities are traditionally kept at arm's length from the president.