World News Update, what you need to know

The US and Britain are considering deepening sanctions against Russia due to its "craven behaviour" in Ukraine, US Secretary of State John Kerry says.

ELSEWHERE:

CANBERRA - An Australian nurse battling the deadly Ebola virus is under observation in the UK for the deadly disease.

LONDON - The families of three missing British schoolgirls believed to have fled to Syria to join the Islamic State group have pleaded for them to return home.

JAKARTA - While Australians Andrew Chan and Myuran Sukumaran wait out a delay in Indonesia's plans to execute them, their predicament has inspired two very different social media campaigns.

BRASILIA - Brazilian President Dilma Rousseff has refused to accept the credentials of the Indonesian ambassador to demonstrate her anger at last month's execution of a Brazilian citizen for drug smuggling.

KABUL - President Barack Obama's new Pentagon chief says the United States is seriously considering slowing the pace of a troop withdrawal from Afghanistan, as the country faces a growing Taliban insurgency.

MIAMI - Two US astronauts have embarked on a six-and-a-half hour spacewalk to route cables outside the International Space Station, after a spacesuit equipment failure delayed the mission.