By Mitch Phillips


LONDON (Reuters) - Tuesday's action at the World Athletics Championships sees two of the most intriguing races of the program as South Africa's Wayde van Niekerk bids for the first half of his 400/200 meters double and Nigel Amos goes for gold in the men's 800m.


World record holder and defending champion Van Niekerk should be unbeatable in the 400m but faces a stiff challenge, not least from Botswanan duo Isaac Makwala and Thebe Baboloki.


Another Botswanan, Amos, will also have to be at his best in the 800m, where a clutch of athletes are suddenly dreaming of glory in the absence of Kenya's injured champion David Rudisha.


Kenya is expected to continue its dominance of the men's 3,000m steeplechase - though American Evan Jager has a chance to cause an upset - and the finals of the men's pole vault and women's javelin also take place.


(Editing by Ken Ferris)