A bubble floats as people blow bubbles during a flash mob at Piazza del Popolo in central Rome on March 21 to welcome spring. Tiziana Fabi/AFP
White whales blow ring-shaped bubbles at the Harbin Polarland, Heilongjiang Province in China on February 2. Reuters
A child blows bubbles with a string-and-straw wand, May 24, at Study Elementary in Fort Wayne, Ind. Children from eight schools participated in the annual Bubble Festival, learning about bubble technology, bubble foam, and bubble walls and windows. They also heard bubble-themed stories. Samuel Hoffman/The Journal Gazette/AP
Japan Aerospace Exploration Agency (JAXA) astronaut Naoko Yamazaki squeezes a water bubble out of her beverage container, showing her refracted image on the deck of space shuttle Discovery, April 12. NASA/Reuters
Allan Santos inspects a fiber optic flower near an LED bubble light at Impact Lighting's Winter Park, Fla., workshop, November 30, 2009. George Skene/Orlando Sentinel/MCT/Newscom/File
Children play with soap bubbles made by hobbyist Zheng Wei at a park in Wuhan, Hubei Province, China, on June 4. Zheng, wants to make the biggest soap bubble in the world by mixing up glycerine and soap water. China Daily/Reuters
A girl selling bubblemaking toys, blows bubbles to attract buyers in Mumbai, India, September 28, 2009. Arko Datta/Reuters/File
Tampa Bay Rays pitcher David Price blows a bubble in the dugout during the 10th inning of a baseball game against the Los Angeles Angels, May 10, in Anaheim, Calif. Denis Poroy/AP
Jose Alberto Sarmiento sits in his 1957 Messerschmitt KR200 three-wheel bubble car on a street in Havana May 20. There are only 36 of the cars remaining in Cuba. Desmond Boylan/Reuters
Earth Day 2009: Wayne Coyne of the Flaming Lips surfs Earth Day On The National Mall crowd in his giant bubble. C. Taylor Crothers. /Planet Green/PRNewsFoto
While Ukraine is not a NATO member, alliance members in Eastern and Central Europe fear they could be Russia's next targets, prompting the 28-nation bloc to seek a robust response.
ByJulie Pace, AP White House Correspondent
Confronted by a Kremlin-backed military offensive in Ukraine, President Barack Obama and Western allies will approve plans this week to position at least 4,000 troops and military equipment in Eastern Europe, bolstering NATO's security commitments to nervous member states near the Russian border.