Britain's Andy Murray faces four-time champion Roger Federer in the Australian Open quarter-finals today.
Tournament favourite Novak Djokovic's three-year reign as champion was ended yesterday when he was knocked out by the Swiss eighth seed Stanislas Wawrinka.
Murray's match is scheduled to begin at around 8.30am UK time.
More top news
Barack Obama has returned to the political spotlight, campaigning for Democratic candidates ahead of upcoming elections.
The prime minister said there was a "clear and urgent imperative" to give new impetus to stalled negotiations.
Pollution claimed nine million lives in 2015, with air pollution from vehicles and factories accounting for 6.5m deaths, researchers found.