Oil dips after three days of gains as OPEC speculation heats up

Crude oil down $1 to $57.97 on the day

There are sudden jitters that OPEC might not formally announced an extension of production cuts at this week's meeting in Vienna. Alternatively, they may not announce curbs through 2018.

Either result would leave the oil market vulnerable.

Breaking just now is a report that senior sources who have spoken to the Petroleum Economist are privately talking down OPEC meeting expectations. They also say Saudi Arabia wants Libya to accept production quotas.

It's late in the game to be trying to get Libya to participate.