Emmy Awards competition will be intensified among TV movie and miniseries performers after two key categories were changed.

The Academy of Television Arts & Sciences said Thursday that it will merge the leading and supporting acting categories for longform programming.

Starting with the 2013 awards, each category for outstanding actor in a miniseries or TV movie and outstanding actress in a miniseries or movie will have six nominees, equal to other performing categories.

Previously, there were four movie and miniseries acting categories with five nominees each.

The TV academy already chipped away at the long-form categories last year, combining the outstanding TV movie and miniseries nominees into one field.

At the 2011 Emmys, Kate Winslet of Mildred Pierce and Barry Pepper of The Kennedys took the acting honours for lead in a miniseries or movie, while supporting awards went to Maggie Smith for Downton Abbey and Guy Pearce for Mildred Pierce.

The academy's decision didn't sit well with at least one channel. Lifetime called it "disappointing," especially in the wake of the consolidation of the movies and miniseries categories, and said award-worthy projects and performances will be slighted.

"Movies and miniseries represent some of television's finest programming and it is our firm belief the industry should honour each category separately," Lifetime Networks programming executive Rob Sharenow said in a statement.

The change announced Thursday coincided with an indication of how robust the competition will be for this year's miniseries and movie Emmys, which will be the last to recognize lead and supporting actors separately.

History channel's Hatfields & McCoys, which broke basic cable ratings records this week, included critically acclaimed performances by leads Kevin Costner and Bill Paxton, as well as by cast members such as Tom Berenger, who likely would compete for supporting actor honours.