Washington ? With higher postage rates set to take effect in two weeks, the U.S. Postal Service is urging Americans to plan ahead and buy stamps now.

New rates boosting first-class mail 3 cents to 37 cents take effect June 30.

Linda Lawrence, supervisor of the downtown Lawrence post office, shows some of the new 37-cent stamps that are available.

The post office says billions of 37-cent stamps have been shipped to its offices across the country.

Five different nondenominated stamps good for the 37-cent rate went on sale June 7. They are a U.S. flag stamp and a set of four antique toys stamps, depicting a mail wagon, steam locomotive, taxicab and fire engine.

The agency also has a 3-cent “makeup rate” stamp featuring a star highlighted in red, white and blue. This stamp allows customers to use up remaining 34-cent stamps they may have on hand.

The stamps also can be purchased at post offices across the country, online at www.usps.com/shop or by calling the Postal Service’s toll-free number, (800) STAMP-24.

Also issued June 7 were the 23-cent Carlsbad Caverns National Park stamped postal card and a 37-cent stamped envelope showing five strands of red, white and blue ribbon forming a white star in the center of the design.

Denominated versions of the antique toys stamps, all bearing the 37-cent rate, will be issued July 26 in Rochester, N.Y.

Scheduled to be issued later this summer are a 60-cent stamp for two-ounce letters, an 83-cent stamp for three ounces, and stamps reflecting other rate changes.