The leading US business group on Friday called France protectionist, after Paris asserted its right to veto any foreign takeover of key French companies.
The US Chamber of Commerce said the move by Paris, announced Thursday as US industrial giant General Electric presses to buy a division of France's Alstom, would not help the country's economy.
"From an open investment policy perspective there is nothing about the motivations behind the recent French decree... that isn't explicitly a mix of industrial policy and protectionism," said Sean Heather, executive director for international policy and antitrust policy at the chamber.
Such moves are "doing nothing to increase the country's competitiveness," he told AFP.
The new rules, which came into effect Friday, allow the government the final say over whether a foreign company -- even one from France's European Union neighbors -- can take over a French firm in the key sectors of energy, transport, water, health and telecommunications.
Economy Minister Arnaud Montebourg called it a move of "economic patriotism."
"These protective measures on France's strategic interests are a renewal of our powers," he told Le Monde newspaper.
Alstom has said it will decide by the end of May on GE's offer of 12.35 billion euros ($17.0 billion) for its energy activities.
But Germany's Seimens has made a counter-bid, and Montebourg has expressed strong reservations about the deal, which involves Alstom's strongest arm.