PARIS-- Walt Disney Co. on Friday tightened its grip on Euro Disney SCA and said it would support a cash injection of up to EUR1.5 billion ($1.6 billion) to fund improvements and reduce debt at the struggling French theme park.

The U.S. company said that Kingdom Holding, the investment firm owned by billionaire Prince al-Waleed bin Talal, had traded 90% of its shares in Euro Disney into Walt Disney stock. Walt Disney said it was buying the stake from Kingdom Holding at EUR2 a share, increasing its shareholding in Euro Disney to 85.7% from 76.7%.

Walt Disney, the company behind the "Star Wars" and "Frozen" franchises, said it then intends to make an offer for all remaining Euro Disney shares at the same price, a 67% premium to Euro Disney's closing share price on Feb. 9. If Disney secures at least a 95% stake following the offer, it plans to delist the company from Euronext Paris.

The pledge won't be the first time Walt Disney has plowed funds into Euro Disney as it struggles to replicate the success of its U.S. theme parks. It follows a 2014 rescue package when the resort was promised EUR1 billion over 10 years to improve its attractions and a financing plan to restructure debt at the French business two years earlier.

Euro Disney raised money from outside shareholders when it went public in 1989 and has remained a separate company from Walt Disney, part-owned by and paying royalties to the U.S. firm. It opened its doors in 1992 but quickly ran into trouble as construction costs soared and operational blunders compounded the debt burden.

Lampooned on cartoon series The Simpsons for a lack of visitors and financial problems, Euro Disney has been a disaster for shareholders. In a cluster of legal disputes playing out in French courts in recent years, a group of activist shareholders alleged that Walt Disney has siphoned off excessive royalties while Euro Disney's assets have been undervalued, in an attempt to drive them out. Euro Disney has said that the claims are baseless.

On Friday, Walt Disney pledged to support a recapitalization of up to EUR1.5 billion for Euro Disney to enable it to "continue implementation of improvements to Disneyland Paris, reduce debt and increase liquidity." The theme park's recent earnings have been pressured by a drop in visitors to Paris following the terror attacks in Nov. 2015 and difficult economic conditions in Europe.

Write to Nick Kostov at Nick.Kostov@wsj.com