Flanagan, 10,000 metres silver medallist at the Beijing 2008 Games, achieved her golden breakthrough in this race last year at the age of 36 as she powered clear of three-time champion Mary Keitany of Kenya in the final miles through Central Park to win in 2hr 26min 53sec.

She faces a huge challenge to retain her title against a strong domestic and foreign field that includes the Kenyan she has faced on 11 occasions in the past without beating, namely Vivian Cheruiyot, the Rio 2016 5,000m champion who won this year’s London Marathon in 2:18.31.

Flanagan has had a low key year so far, finishing sixth in the rain-swept Boston Marathon in April, her last completed race.

“My fitness is good, I couldn’t ask for better,” she said.

“Over the past two years I’ve acted as if each marathon is my last, not knowing where it’s going to take me.

“Until I cross the finish line, I honestly don’t know.”

Cheruiyot, 35, indicated preparations were going well by winning the Great North Run in Newcastle in September, clocking 1:07:43 for the half marathon.

However, this will be Cheruiyot’s first time tackling the New York City Marathon while her compatriot, Keitany, knows the course well as a three-time winner of the race between 2014 and 2016.

Home runner Desiree Linden, who had her own marathon breakthrough by winning in Boston, can be expected to figure significantly, as can fellow American Molly Huddle, who holds the US records at the 10,000m and half marathon.

Ethiopian duo Mamitu Daska and Netsanet Guduta also hold strong claims of netting their nation a first women’s title since Derartu Tulu in 2009.

For Kamworor, who beat compatriot and former world record holder Wilson Kipsang by three seconds last year as he finished in 2:10.53, the prospects of a successful defence look strong, given that he has been unbeaten this year.

A training partner of Eliud Kipchoge, who set the marathon world record of 2:01:39 in Berlin in September, Kamworor is confident of his form ahead of tomorrow’s race.

“My preparation is going as well as last year – it’s almost the same and so far, so good,” he said.

 “I believe in what I have done and I am ready to race. If I win, I will be the happiest man in the world because I will have won everything this year.”

Standing in his way is a formidable line-up of East Africans, chief among them Shura Kitata, who produced an outstanding showing to finish second at the London Marathon in April, just 32 seconds behind Kipchoge in a personal best of 2:04:49.

Kenya’s Daniel Wanjiru should also make his presence felt - the 2017 London Marathon champion is racing here for the first time.

Ethiopia’s Lelisa Desisa was runner-up in New York in 2016 and the two-time Boston Marathon champion will be hoping to go one better this time.

The fastest athlete in the race is Ethiopia’s Tamirat Tola, who ran a personal best of 2:04:06 to finish third at the Dubai Marathon in January.

The US challenge will be spear-headed by 43-year-old former world 5000m champion Bernard Lagat, who will make his marathon debut and is targeting Meb Keflezighi’s US masters’ record of 2:12:20.