The Boston Marathon attracts runners from the United States and all over the world who sometimes train for years to qualify, with most competitors required to post fast times in other 26.2 mile races to earn a spot in the 27,000-runner field.

"The opportunity to run down Boylston Street and to cross the finish line amid thousands of spectators is a significant part of the entire Boston Marathon experience," said Tom Grilk, executive director of the Boston Athletic Association, which organizes the race. "With the opportunity to return and participate in 2014, we look forward to inviting back these athletes and we expect that most will renew their marathon training commitment."

About 5,600 entrants will be eligible for return invites in 2014, the 118th running of the Boston marathon, organizers said.

This year's race was halted at 2:50 p.m. EDT on April 15 when two pressure cooker bombs left at the finish line exploded in a crowd of thousands of spectators and athletes, killing three people and injuring 264 others.

Runners were rushed off the course as emergency responders searched to see if any additional explosive device had been planted, but none were found.

Two ethnic Chechen brothers who lived in neighboring Cambridge, Massachusetts, were accused by the FBI of planting the bombs. The younger of the pair, 19-year-old Dzhokhar Tsarnaev, was arrested on April 19 after a day-long manhunt that shut most of the Boston area, while his older brother, 26-year-old Tamerlan, died in an earlier gunbattle with police.

CBS News reported on Thursday that Dzhokhar Tsarnaev left a handwritten message describing the attack as retribution for U.S. wars in Muslim countries and called his brother a martyr.

(Reporting by Scott Malone; Editing by Grant McCool)