Christina Aguilera will not tour this summer as she previously planned. The pop star has instead opted to wait until sometime in 2011 to begin her North American concert schedule.

The 20-city summer tour was supposed to begin July 15 at Mohegan Sun Arena in Uncasville, CT. Tour promoter Live Nation attributed the year-long tour delay to Aguilera's "prior commitments" for promoting her new album "Bionic" and upcoming film "Burlesque."

Christina Augilera is said to be four months pregnant and was ordered to cancel two of her world tour dates after collapsing.

The 'dirrty' vocalist, reportedly experienced breathing difficulties during a performance in Melbourne, Australia, last Friday. It was not determined if the collapse was attributed to the alleged pregnancy or if it was just a case of exhaustion.

Although she reportedly was able to finish the concert, the sexy star was forced to miss some songs and an encore. Medical Technicians were summoned to the concert site and after treating Christina, they recommended that she cancel her two remaining Melbourne shows and advised her to rest.

Christina, who has yet to confirm or deny the pregnancy herself, apologized to her fans, claiming she was fighting a bout with the flu. "I want to personally apologize to all of my fans. I am truly disappointed that I won't be able to share my show with you all." she said. . .