Christie's employees hang the portrait of Count John McCormackNiall Carson/PA

A painting of Ireland’s most celebrated tenor will go up for auction next month, and art collectors from around the world are prepping for a bidding war.

The painting, by Dublin artist Sir William Orpen, depicts Athlone native John McCormack, “Ireland’s Pavarotti,” who in 1932, sang for two million people in Dublin’s Phoenix Park.

The McCormack painting is expected to go for as much as €678,000 (about $879,364) at the Irish and Sporting Art sale at Christie’s in London on May 7 and 8.

Interest has peaked from art collectors not just from Ireland, but from the Vatican and the U.S., where the famous opera singer lived for many years.

Collectors from the U.S. and the E.U. are expected to up the ante on the bidding due to the decreased value of the sterling.

The auctions will include the general Irish sale, as well as an auction from the Glin Castle collection in County Limerick and the Vincent Ferguson collection.

The auctions are expected to bring in around €4.5m ($5.8m) to €6.7m ($8.7m).