An oil rig is shown in this file photo.

Brent crude futures fell $1 to $97.85 a barrel on Tuesday as worries about the euro zone debt crisis weighed on expectations for global oil demand growth.

Despite oil falling to a 16-month low on Monday, prices near $100 a barrel are still a threat to a slowing global economy, the International Energy Agency (IEA) executive director Maria van der Hoeven said on Tuesday.

On Tuesday, striking a similarly bearish note for oil markets, Royal Dutch Shell Chief Executive Peter Voser said oil prices were likely to continue to decline well into the second half of the year. - Reuters