Ireland players celebrate after defeating Samoa in their Rugby World Cup Pool A game at Fukuoka Hakatanomori Stadium. Photo: AP Photo/Aaron Favila

BRUSSELS - While British lawmakers agonise in parliament on Saturday over whether to approve a last-minute European Union divorce deal, one interested onlooker will be watching a different television channel.

Irish Prime Minister Leo Varadkar, who played a key role in striking the Brexit agreement this week, said he will instead be glued to Ireland's Rugby World Cup quarter-final against New Zealand in Japan.

British Prime Minister Boris Johnson will address lawmakers at 0830 GMT on Saturday to kick off an extraordinary Saturday sitting, the first since 1982, with the teams set to take the field at Tokyo Stadium at 1015 GMT.

"My plans for tomorrow are to watch the rugby match," Varadkar, a keen Ireland and Leinster fan who has togged out for the Irish parliament's rugby team, told a news conference in Brussels. "Hopefully that will be successful for Ireland and then we'll see what happens in the House of Commons," he said.

Ireland's coach Joe Schmidt watches as his players warm up ahead of the Rugby World Cup Pool A game at Kobe Misaki Stadium between Ireland and Russia. Photo: AP Photo/Christophe Ena

Varadkar moved a televised address to his Fine Gael party's annual conference away from its regular prime time spot last year because it clashed with live coverage of Ireland's last test match against world champions New Zealand.

Ireland beat the All Blacks 16-9 that day, just their second victory in 31 attempts, as their prime minister watched via a big screen at the conference. 

Reuters