At the world's top auction houses, sellers put paintings on the block, but it's the art handlers who actually get them there.

Handlers at Sotheby's are saying the company is trying to shortchange their role in the process by asking for concessions in their contracts. With the art handlers' union raising the specter of a strike, the two sides are set to meet Monday in an attempt to hammer out a deal, according to the union.

The contract between the handlers' union and the auction house expired at the start of the month, and they have been unable to reach a new agreement.

Sotheby's wants to offer buyouts and replace some of the unionized art handlers with nonunion labor, according to Teamsters Local 814 President Jason Ide.

The union, however, says the auction house shouldn't be asking for concessions on the heels of the second-most-profitable period in its history.

Sotheby's sales increased by 74%, to $4.8 billion, during 2010, with $161 million in net income and significant upticks in executive pay. President and Chief Executive William Ruprecht received nearly $6 million in salary, stock awards and other compensation, representing a more than 150% increase versus his 2009 package.

Mr. Ide, himself a former Sotheby's art handler, said the company's achievement should allow it to avoid asking for cuts, such as a reduction in the workweek, By not doing so it would be jeopardizing its "longstanding relationship" with the union, he said.

"They've had an amazing year and that's a testament to the success of their business, but it's also a testament to the abilities" of handlers and other employees, Mr. Ide said.