Taylor Swift adds Haim to '1989' tour

Taylor Swift's 1989 World Tour just keeps getting better and better.

The tour, which has its first U.S. date May 20 in Bossier City, La., already will feature Riptide singer Vance Joy and Shawn Mendes as support on most dates. On Sunday, Swift announced via Twitter that she's adding Haim for several dates.

The sibling trio, who are competing for a best-new-artist Grammy next Sunday, will play four stadiums with Swift in July, followed by arena shows in Los Angeles, Nashville and St. Louis.

The following tour dates will include Haim as a special guest.

July 10-11 - MetLife Stadium, East Rutherford, N.J.

July 13-14 - Nationals Park, Washington, D.C.

July 18-19 - Soldier Field, Chicago

July 24-25 - Gillette Stadium, Foxborough, Mass.

Aug. 21-22 - Staples Center, Los Angeles

Aug. 24-26 - Staples Center, Los Angeles

Sept. 25-26 - Bridgestone Arena, Nashville

Sept. 28-29 - Scottrade Center, St. Louis