By Neil Robinson

LONDON (Reuters) - Seb Coe hailed the inaugural two-day Athletics World Cup at the London Stadium, which was won by the United States on Sunday, as a success and said other cities have expressed interest in hosting what is expected to be a biennial event.

The U.S. won six of Sunday's 15 events to extend their 24-point overnight lead and finish on 219 points, 57 points ahead of second-placed Poland, and claim the $450,000 prize money.

Great Britain & Northern Ireland finished third on 155, two points clear of fourth-placed Jamaica.

Despite criticism of the format, a half-empty stadium and the absence of many of the world's top athletes, Coe said he had already had discussions about other cities taking on the event.

"Other cities have expressed an interest and I have had several conversations," he told Reuters in a phone interview, although he could not confirm British media reports that China is in line to take the event in 2020 and the U.S. in 2022.

Coe said he was delighted with the innovative format which saw eight countries compete over track and field events up to 1,500m in a glitzy format with loud music and shootout finals.

"I did challenge federations to challenge themselves and I am delighted they took up that challenge," he said. "We will review everything. There are clues we can draw from."

But he refused to criticise athletes who did not turn up, saying those were individual decisions.

American captain Queen Harrison lifted the $250,000 Global Platinum Trophy, claimed to be the most expensive in sport.

AMERICAN SUCCESS

Pole vault world champion Sam Kendricks had set the tone for America's successful evening by winning the opening event, with 400m runner Paul Dedewo, 400m hurdler Kenny Selmon, women's 800m runner Raevyn Rogers, high jumper Vashti Cunningham and the men's 4x400m relay team the other winners for the U.S..

But questions remained about many aspects of the event, not least its timing. To schedule aa Athletics World Cup on the weekend that soccer's global showpiece also peaked with the final in Moscow - before a worldwide audience of one billion - always looked like an act of astonishing bravery.

Organisers UK Athletics claimed at least 25,000 packed into the London Stadium on Sunday.

With about 30,000 present on Saturday's first day, the overall figure is well down on the 110,000 originally hoped for, but there were still high points for an enthusiastic crowd with the biggest cheer of the night going to the British 4x100m women's relay team, who won the penultimate race.

Organisers said they will take time to assess the event but most athletes enjoyed the atmosphere at the same stadium which hosted the 2012 Olympic Games and 2017 World Championships.

"For me it is a good competition," said Poland's Olympic and world championships bronze medallist Wojciech Nowicki, who won the hammer with a throw of 77.94m. "The team aspect was very important for me."

American 800m women winner Rogers said: "It reminds me of the collegiate setting. Everyone has to work together and perform in their own event and do the best they can and respond to things which don't go our way."

When launched earlier this year, the World Cup was hailed as the "magic bullet" for the sport, with athletes vying for one of the 102 medals on offer in a series of shootout finals.

But any hopes the organisers harboured of their competition establishing "the best country in the world" were rendered meaningless by the absence of most of the world's top athletes, many of whom opted instead to compete before far smaller crowds in Friday's Diamond League event in Rabat.

World 100m champion Justin Gatlin, world indoor 60m record holder Christian Coleman and Diamond League 100m leader Ronnie Baker all gave it a wide berth, with South Africa's Caster Semenya pulling out at the last minute to head for Morocco.

Britain's best athletes, including 100m national record holder Dina Asher-Smith, were also no-shows, ensuring that the event was stripped of many potential high points.

(Reporting by Neil Robinson; Editing by Ken Ferris)