Oil prices hit reverse Tuesday, snapping two days of gains as dealers awaited this week’s US crude inventories data and Britain’s critical in-out EU membership referendum.

Oil prices hit reverse Tuesday, snapping two days of gains as dealers awaited this week's US crude inventories data and Britain's critical in-out EU membership referendum.

At about 1100 GMT, world benchmark contract Brent North Sea crude for delivery in August was down 66 cents to $49.99 a barrel.

US benchmark West Texas Intermediate for July delivery shed 60 cents to $48.77 a barrel compared with Monday's close.

Crude futures had jumped Monday in volatile trade on rising expectations that Britain would vote to remain in the European Union on Thursday.

Polls in Britain showed on Monday the "Remain" camp gaining ground against "Leave" supporters, putting the race neck and neck just three days before the referendum.

However, new polls out Tuesday showed a razor-tight race 48 hours ahead of the vote.

"Uncertainty around the outcome of the EU referendum is... likely to have resulted in a trimming of stretched long positions in the oil market," British bank Barclays said in a note, projecting a "volatile path ahead for oil prices" over the second half of the year.

"In the event that the UK votes to leave the EU, we expect global economic growth to stagnate, and that factor would have the most influential impact on oil prices over the next 4-6 quarters," it added.

Traders are also waiting for the weekly US crude inventories report due Wednesday to gauge demand in the world's top oil consuming nation, as well as a testimony by Federal Reserve chief Janet Yellen for clues on the timing of a US interest rate increase.

A US interest rate increase tends to push the dollar higher, making oil more expensive for buyers using other currencies. That tends to weigh on oil prices.