The battle at Newell Brands is heating up.

Activist investor Carl Icahn has upped his stake in the Elmer’s glue maker to 6.9 percent, according to a Friday regulatory filing.

The filing comes weeks after The Post reported exclusively that Icahn owned a Newell stake.

Icahn’s enlarged stake injects an extra dose of uncertainty at Newell, which has seen five board members exit and is in the midst of a proxy battle with Jeffrey Smith’s activist hedge fund Starboard Value.

Icahn is continuing to assess Starboard’s proxy contest and bought shares to influence the future of Newell, “whichever side we join,” the filing said.

Newell said it welcomes “open and active engagement with our shareholders.”