WASHINGTON — In a major boost for President Joe Biden’s pledge to eliminate gas-powered vehicles from the sprawling federal fleet, the Postal Service said Tuesday it will sharply increase the number of electric-powered delivery trucks — and will go all-electric for new purchases starting in 2026. “This is the Biden climate strategy on wheels and the U.S. Postal Service delivering for the American people,” said White House climate adviser Ali Zaidi. The U.S. government operates the largest vehicle fleet in the world, and the Postal Service is the largest fleet in the federal government with more than 220,000 vehicles, one-third of the overall U.S. fleet.