DENVER (AP) ― Christie’s and Sotheby’s auction houses are fighting over the sale of four paintings by late American abstract expressionist Clyfford Still, each claiming it can offer a better deal.

The city and county of Denver hopes to fetch at least $25 million for a new Clyfford Still Museum scheduled to open this year. To pay for the museum, the city chose to sell four of the 825 paintings headed for the museum. Still’s estate has yet to be distributed, but a court agreed to the transfer of the four paintings pending a formal decision on the sale.

Sotheby’s won the bid pending Denver City Council approval. Christie’s is fighting the decision, claiming Sotheby’s proposal was deficient and the city could have struck a better deal.

Under the agreement, Sotheby’s contract requires a minimum net to the museum of $25 million. Sotheby’s could get a 5 percent commission, or $7.5 million, whichever is less, if the works are sold to another museum. Or it could get at the most a $15 million commission if the works are sold to private buyers at auction.

In a statement, Christie’s said: “We are concerned that the process of awarding of the contract was arbitrary and capricious. The public will not be served by rushing into a binding sale agreement before a full and complete consideration of proposals for sale. Based upon our review of the publicly available documents, we had offered a considerably more favorable bid to the city and its citizens.”

Christie’s, which is based in London, has hired lawyers and a lobbying firm to try to stop the arrangement before Monday, when the City Council begins considering the contract.

Lobbyist David Cole, whose firm represents Christie’s, has asked the city to turn over documents related to the decision.

“They believe it was an egregious decision. They were literally scratching their heads at the contract. In their minds, (the Sotheby’s) proposal was so totally deficient compared to what could have been done,” Cole said.

Sotheby’s disagrees.

“It is disappointing that one of our competitors has now challenged the city’s careful and considered selection process. Having competed for many opportunities, my view has always been that even when we are not chosen, we should wish the client well and hope that their works sell for strong prices,” said Sotheby’s chief executive Bill Ruprecht.

According to the Denver Post (http://bit.ly/pSqEWa ), this kind of public squabbling from two major art-auction houses is unusual.

“It has been a very secretive world. I think it’s probably bad for the big companies to air their grievances in public. But it may be good for smaller companies,” said Peter Loughrey, director of Los Angeles Modern Auctions.

Jan Brennan, director of cultural programs for Denver’s Office of Cultural Affairs, said the bidding was fair.

“Certainly, the financial terms were most significant. But there were other things ― qualifications of the auction house, expertise of the staff, proposed sales approach, estimates, their experience in selling fine art as well as (working) with municipal entities,” she said.