DENVER (AP) -- Mitt Romney's campaign is blocking reporters from covering GOP vice presidential candidate Paul Ryan's first meeting with donors in Las Vegas.

Tuesday night's event at The Venetian hotel is expected to draw casino owner and Republican mega-donor Sheldon Adelson.

The decision to block access marks a break from rules previously established by Romney's campaign.

Reporters usually are allowed to cover President Barack Obama's fundraisers when they are held in public venues.

A Romney aide who was not authorized to speak for the record said the event is closed to the media because it is a "finance meeting" instead of a fundraiser.

But Ryan attended two Denver-area fundraisers on Monday night where media coverage also was prohibited.