OSLO, June 5 (Reuters) - Norwegian oil and gas workers and their employers have extended wage negotiations past a midnight deadline in a bid to avert a strike that could cut output by 45,500 barrels of oil equivalent per day, an industry official said on Friday.

Just over 600 workers out of roughly 8,100 employees on offshore platforms plan to strike from Friday onwards if the annual pay negotiations fail, trade unions Styrke, Safe and Lederne have said.

The deadline for the talks had originally been set to midnight on Thursday local time (2200 GMT).