By Foo Yun Chee and Benoit Van Overstraeten

BRUSSELS (Reuters) -Candy maker Mars' takeover of Pringles maker Kellanova was cleared by U.S. antitrust regulators on Wednesday, but their EU counterparts opened a full-scale investigation into the $36 billion deal, saying it could lead to price hikes.

President Donald Trump's antitrust enforcers, including Federal Trade Commission Chairman Andrew Ferguson, have said they will not hesitate to block deals that harm competition in ways that hurt consumers, but also vowed not to stop deals that do not pose such concerns.

"Our job is to determine whether there is a violation of American law that we can prove in court. And once we’ve concluded there is not, our job is to get out of the way," Bureau of Competition Director Daniel Guarnera said in an FTC statement announcing the early termination of its review of the deal. The deal did not meet the standard for an anticompetitive merger, the FTC said.

Mars said it was pleased by the U.S. decision and that the deal had received all regulatory clearances aside from the EU. It said it expected the deal to close towards the end of 2025.

Kellanova did not immediately respond to a request for comment on the U.S. approval, which was made outside regular business hours.

The EU's move could force Mars to divest assets to address the European competition concerns or risk the deal being blocked. The EU warned that prices may rise as the deal will boost Mars' negotiating power with retailers.

Mars said after the EU move that it was disappointed with the EU's decision but it remained optimistic over the outcome of the transaction.

"We remain confident the pending combination of Mars Snacking and Kellanova's complementary footprints and portfolios will deliver more choice and innovation to consumers," said Mars in a statement.

"We look forward to delivering the benefits of the pending transaction to all Mars and Kellanova stakeholders," it added.

Mars announced the deal last August, among the biggest in the sector, that would bring brands from M&Ms, Snickers and Whiskas to Pringles, Pop-Tarts and Kellogg cereals under one roof.

Combined, Mars and Kellanova would account for roughly 12% of the U.S. snacking and candy industry, according to market share data from NielsenIQ. This would still leave the market with competitors including PepsiCo PEP.O, Kraft Heinz KHC.O, Mondelez MDLZ.O, Hershey HSY.N, General Mills GIS.N and others.

Consumer advocacy groups had called on the FTC to investigate the deal last year, likening it to grocery chain Kroger's proposed acquisition of rival Albertson's, and raising concerns it would lead to higher grocery prices. Some experts at the time the deal was announced noted a limited overlap among their offerings. 

The EU competition enforcer said the deal would boost Mars' product portfolio, giving it increased leverage to extract higher prices during negotiations with retailers and in turn would lead to higher prices for consumers.

It said both companies have a strong market position in several product markets in multiple EU countries due to their brands seen as must-have for consumers.

The Commission also cited concerns from some European retailers about Mars' increased bargaining power and that they may be forced to accept higher prices, in order to avoid not being able to offer the products of Mars and Kellanova.

"As inflation-hit food prices remain high across Europe, it is essential to ensure that this acquisition does not further drive up the cost of shopping baskets," EU antitrust chief Teresa Ribera said in a statement.

The Commission set an Oct. 31 deadline for its decision. Reuters exclusively reported on June 18 that the deal would trigger intensive EU regulatory scrutiny.

European retailers have voiced worries about the power of large international suppliers of branded packaged goods and the high concentration levels in products such as breakfast cereals, carbonated drinks, confectionery and frozen desserts.

(Reporting by Foo Yun Chee; Additional reporting by Chandni Shah in Bengaluru; Editing by Benoit Van Overstraeten, Sudip Kar-Gupta and Sonali Paul)