Big day for UK at Olympics
02:05 - Source: CNN

Story highlights

American Michael Phelps earns his 18th gold medal in what's expected to be his last race

Sun Yang adds to China's growing gold tally with a win in the men's 1500-meter freestyle

Team USA just squeaks past Lithuania in the men's basketball competition

London CNN  — 

Olympics fans will revel in track and field’s most anticipated event Sunday, and the men’s 100 meters will not lack for drama as Jamaican sprinter Usain Bolt attempts to defend his title against his fellow countryman.

Bolt became a household name with his gold medal win in the 2008 Beijing Games. His compatriot, Yohan Blake, is proving to be his main competition as they face off Sunday evening . Americans Tyson Gay, Justin Gatlin and Ryan Bailey will also be in the men’s 100 final.

Among the first events of the day is the women’s marathon, which will pit favorites Mary Keitany from Kenya against Russian Liliya Shobukhova.

Noticeably absent from the race will be world record holder Paula Radcliffe, from Great Britain, who withdrew citing a recent injury.

In one of tennis’ most anticipated showdowns, World No. 1 Roger Federer faces hometown favorite Andy Murray, whom he defeated at Wimbledon last month.

Federer, who has 17 grand slam titles under his belt, is hoping to complete a career golden grand slam.

Only Andre Agassi and Rafael Nadal have achieved the feat of claiming a full set of grand slam titles and backed it it with Olympic gold in the singles.

Sunday’s events follow an action-packed Saturday that saw the host nation rake in six wins, bringing its gold medal count to 14.

Only China and the United States have more.

Jessica Ennis earned the heptathlon gold, Greg Rutherford scored a long jump win and Mo Farah’s sprint to victory made him the first British runner ever to do so in the 10,000 meter competition.

Overall, China leads the gold medal count with 30 and the total medal count with 61. The United States trails with 28 gold and 60 total.

But history on Saturday also favored the leaders, as the most decorated Olympian of all time tallied another win with his American teammates in the 4 x 100-meter medley relay, handing Michael Phelps his 18th gold medal in the last race of his storied swimming career.

The U.S. win put an already unsurpassed Phelps at 22 total medals over three Olympic Games: 18 gold, two silver and two bronze. Japan placed second in Saturday’s race, while Australia finished third.

In the last day of London’s swimming competition, the American women won the 4x100-meter medley relay race, setting a new world record with a time of 3:52.05. Australia netted silver.

Sun Yang also added to China’s growing gold tally with a win in the men’s 1500-meter freestyle. Ryan Cochrane of Canada finished second, while Oussama Mellouli of Tunisia took bronze.

But on the hardwood Saturday, U.S. Olympic command seemed far less convincing.

Team USA squeaked past Lithuania in a preliminary round basketball contest, winning by just five points after trailing by two in the waning minutes of the fourth quarter – the first scare for the favored American squad after a series of dominating performances that had bolstered an aura of invincibility.

Elsewhere in London, Serena Williams completed a “career Golden Slam” at the 2012 Games, adding for the United States an Olympic women’s singles tennis gold medal to her four tennis major titles.

Also on the track, double-amputee sprinter Oscar Pistorius, who runs on special carbon fiber blades and is nicknamed “The Blade Runner,” came in an impressive second in his heat of the men’s individual 400-meter race, thus qualifying for Sunday’s semifinals.

He is the first person to compete in the able-bodied Olympics using prosthetic legs – and he will also compete in the Paralympics later this summer.

CNN’s Steve Almasy and Dominque Van Heerden contributed to this report.