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The clock is counting down to the start of this year's Bank of America Chicago Marathon.

The city's biggest race of the year steps off at 7:30 a.m. Sunday in Grant Park, unleashing some 45,000 runners into 29 neighborhoods for 26.2 miles. An estimated 1.7 spectators are expected to line roadways, cheering, holding signs and yelling words of encouragement.
 
This year's field of runners will be led by a group of 30 elite participants, including past marathon winners, Olympians and world-record setters. 

Less than 48 hours before the start of the race, the top elites talked to reporters about their preparation and expectations for the race.

Michigan runner Dathan Ritzenhein, the third-fastest American marathoner of all time, is among those expected to place high. Ritzenhein finished ninth last year among the men and said he has some new goals this time around.

"I'd like to go out faster than I did last year," he said, "and ... hopefully I can come home strong, even stronger than last year. I think I can run a lot faster than I did in 2012."

Matt Tegenkamp, making his marathon debut this year, said he's ready to put aside all nervousness and see what he can do.

"I said I wasn't really going to pay attention to what Sunday was going to bring until I arrived in Chicago," Tegenkamp said, "so as we keep moving forward there will be more and more butterflies building but it'll be a good thing. It's just an anticipation of the unknown and really looking forward to tackling a new challenge."

All eyes also are on two women who finished neck-and-neck in 2012 with just one second separating the two. Atsede Baysa, who won in 2012, and Rita Jeptoo, who finished a very close second, are back to duel it out again this year.

Marathon organizers said the much-publicized new security measures are in place and the city is ready for race day. After the Boston Marathon bombings, the Chicago Marathon stepped up security, increasing checkpoints, banning spectators from the start and finish lines, and requiring runners to pick up their own race-day packets.

At this point, though, Executive Director Carey Pinkowski said the focus is on the runners.

"The atmosphere is amazing," Pinkowski said. "It's a year planning that comes down to Marathon Sunday. We have so many participants that have so many individual goals."