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Feb 17 (Reuters) - Activist investor Jana Partners has built a stake in Fiserv FISV.O and is pressing the payments company to pursue steps to lift its lagging share price, the Wall Street Journal reported on Tuesday, citing people familiar with the matter.

The size of Jana's stake, and whether the activist investor intends to seek board seats at Fiserv could not be determined, the report said.

Shares of the company were up 6.5% in premarket trading. The stock slumped more than 67% in 2025 and has declined nearly 12% year to date, as of last close.

"During the past several months, we have engaged with many of our shareholders, including JANA Partners. We value shareholder perspectives as we drive progress through our One Fiserv action plan," Fiserv said in a statement.

Jana partners did not immediately respond to Reuters' request for comment.

The firm conducted an extensive review last year and CEO Mike Lyons has since emphasized the need to strengthen forecasting rigor and reduce reliance on short-term growth initiatives.

Fiserv expects 2026 to be a transitional year, as it invests in key strategic areas to fix gaps and improve client service.