The United States is coming out this Thursday with another Love stamp, this time for puppy love. The next day the United Nations is coming out with its first issue of the year, devoted to Africa. Revenue from the U.N. stamps is earmarked for aid in that continent.

The three stamps in the new U.N. issue were all done by artists of Ethiopia and have great impact because of their unusual conceptions and vivid colors.

The World Federation of United Nations Associations, which traditionally accompanies new U.N. issues with cacheted covers and prints, is contributing for the occasion an oil painting by Rokhaya Sarre, wife of Senegal's representative to the United Nations. The work, entitled, "Prayers for Africa," depicts a barren landscape.

The first-day ceremony for the new Love stamp will be in New York, with Muppet creator Jim Henson and Rowlf the Dog, one of his characters, taking part.

At the top of the stamp is the word "Love" in magenta capitals, with the postal data in black just below it. Below that is a cartoon puppy, its head tilted.

The vertical stamp, designed by Saul Mandel, a graphic artist in Jericho, N.Y., has been produced by gravure in five colors: yellow, magenta, cyan, black and violet. There is a five-digit plate number on every post office pane of 50 stamps.

Collectors of first-day-of-issue cancellations have the customary 30-day grace period for sending in orders -- which must be postmarked no later than March 1 -- and the usual alternative ways of ordering.

Collectors affixing stamps themselves on their envelopes, which must bear addresses, should send them to Customer-Affixed Envelopes, Love Stamp, Postmaster, New York, N.Y. 10001-9991.

Collectors preferring full processing by the Postal Service should send their envelopes, which must be addressed, to Love Stamp, Postmaster, New York, N.Y. 10001-9992. Ththur Bartow commemorative. Philatelic Service, Canada Post, National Philatelic Center, Antigonish, Nova Scotia, Canada B2G 2R8.