President Donald Trump moved Tuesday to make good on his emblematic pledge to "Buy American, Hire American" by tightening skilled-worker visa rules, but his room for maneuver remains limited without wider congressional reform.

Speaking in Kenosha, Wisconsin -- one of the states that carried him to his upset victory last November -- Trump vowed: "We're going to do everything in our power to make sure more products are stamped with those wonderful words, 'Made in the USA.'"

Like many of Trump's executive orders to date, his newest decree will have little practical impact, but sends a signal for government agencies to come forward with ideas for reforming the country's H-1B visa system.

Trump is looking to stamp out "abuses" of the time-limited work permits, which are pervasive in the US high-tech sector, as a first step towards reforming the regime.

Intended for scientists, engineers and computer programmers, H-1B visas have become an important gateway for the many Indians drawn to Silicon Valley. The United States issues 85,000 each year.

Trump's decree namely instructs the Labor, Justice and Homeland Security departments to tackle abuses and draw up reforms aimed at bringing the program back to its original intent: awarding visas to the most skilled and highly paid applicants.

The Trump administration argues that the current system has led to a "flood" of relatively low-wage, low-skill workers in the tech sector -- and in doing so has harmed American workers.

"We believe jobs must be offered to American workers first," Trump said.

The US Chamber of Commerce voiced immediate reservations: While it agreed there was room for improvement of the H-1B program, it warned the Trump administration not to do away with it altogether.

"It would be a mistake to close the door on high-skilled workers from around the world who can contribute to American businesses' growth and expansion and make the US more competitive around the world," the business lobby said in a statement.

The White House sees the decree as a way to spur momentum towards a broader congressional reform of the H-1B scheme -- whose outline remains unclear.

"This is a transitional step to get towards a more skill-based and merit-based version," a US official told AFP. "There is a lot we can do administratively, and the rest will be done hopefully legislatively."

In his maiden speech to Congress, on March 1, Trump had proposed introducing an Australian-style merit-based system to reduce the flow of unskilled workers into the United States.

- Seeking momentum -

Trump's new decree also includes a "Buy American" component, calling for stricter implementation of existing laws that are intended to favor US-manufactured goods in public tenders.

Without making specific new announcements, the Republican president once more pointed the finger at the North American Free Trade Agreement between the US, Canada and Mexico, dubbing it "a complete and total disaster."

"It's been very, very bad for our companies and for our workers and we're going to make some very big changes or we are going to get rid of NAFTA for once and for all," he warned.

As Trump's presidency nears the symbolic 100-day mark, the 70-year-old leader is looking to regain momentum on the domestic front after his flagship travel ban was blocked in court, and his vaunted health reform foundered in Congress.

Trump's promise of an ambitious tax reform -- another central campaign pledge that would notably involve slashing corporate taxes -- is also struggling to take shape.

"Our tax reform and tax plan is coming along very well," Trump said in Wisconsin. "It's going to be out very soon."

But Treasury Secretary Steven Mnuchin acknowledged in the Financial Times earlier Tuesday the reform would likely be delayed, calling the target of getting it through Congress before August "highly aggressive to not realistic at this point."