Budapest, Aug 20 : The United States won the mixed 4x400m relay at the World Athletics Championships here on Saturday night, improving their own world record to 3:08.80 after the Netherlands' world indoor 400m record-holder Femke Bol fell three strides from the finish line, having appeared on the brink of anchoring her team to victory. It was not the only dramatic moment on an eventful opening day of the competition. It started with the greatest depth men's 20km race walk in championship history, won by Spain's Alvaro Martin and culminated in the sensational 4x400 mixed relay. In between those, Ryan Crouser successfully defended his shot put title with a championship record of 23.51m, and Gudaf Tsegay led an Ethiopian sweep of the medals in the women's 10,000m. But falls from two prominent Dutch athletes -' first by Sifan Hassan in the 10,000m and then by Femke Bol in the mixed 4x400m ' proved the two big talking points of the dramatic evening. Handed the baton with a narrow lead, Bol could not hold it to the finish as USA's Alexis Holmes, gritting her teeth, moved up to challenge her over the final 50 metres. Bol fell and landed very close to the spot where her Dutch teammate Sifan Hassan had fallen face down as she appeared ready to win the preceding women's 10,000m final. The new mark set by Justin Robinson, Rosey Effiong, Matthew Boling and Holmes bettered the 3:09.34 set by the United States in the Doha 2019 World Championships when the mixed 4x400 relay was made its debut. Great Britain took silver in a national record of 3:11.06, with bronze going to Czechia in 3:11.98 - also a national record. The women's 10,000-metre race was no less dramatic as Gudaf Tsegay of Ethiopia and Sifan Hassan of the Netherlands raced to the finish, shoulder to shoulder with their arms pumping and their eyes fixed on the line. Both were chasing 10,000m gold in a thrilling first-track final on the first day at Budapest. Two of the fastest-ever women runners on this distance were locked in a fierce fight before disaster struck the Dutch hopes. Just metres from the finish line, Hassan, the Olympic champion, fell and her dreams of another global medal treble went crashing down with her. As Hassan stumbled, Tsegay remained resolute. The world 5000m champion from Oregon last year gritted her teeth and ended up adding a maiden 10,000m title to her burgeoning global medal haul, clocking 31:27.18 to lead an Ethiopian medal sweep ahead of world record-holder and defending champion Letesenbet Gidey, and world indoor medallist Ejgayehu Taye. American Ryan Crouser overcame all possible hurdles as he retained the world title he claimed in his home state of Oregon last year ' in the process becoming the first man in history to land double world and Olympic shot-put titles. Leading from the first throw of the competition, Crouser twice bettered the championship record he set in Oregon in 2022 -' with 22.98m in round two, and then with a stunning 23.51m in round six, just five centimetres shy of the world record he nailed in Los Angeles in May this year. Italian Leonardo Fabbri claimed silver with a lifetime best of 22.34m while American Joe Kovacs took the bronze medal with a distance of 22.12m. /IANS