The US Republican vice-presidential candidate, Sarah Palin, has said it is the agreement between Nato allies if one country is attacked, other is expected to be called upon and help. Speaking to US TV, Mrs Palin said she was "ready" to serve the US as deputy to John McCain. On foreign affairs, the 44-year-old Alaska governor said she backed Nato membership for Ukraine and Georgia. Speaking to troops being sent to Iraq, she said they were on a righteous cause and they would succeed in their mission.