The European Commission may try to force Apple into dropping the Lightning connector for USB charging.

The commission will investigate how it can push the smartphone industry to adopt one universal battery charger, the EU's competition chief, Margrethe Vestager, said earlier this month.

For the past decade, the commission has been using voluntary agreements to encourage the tech industry to get behind a universal charger. But Vestager said it's time for EU regulators to consider new tactics.

"Given the unsatisfactory progress with this voluntary approach, the Commission will shortly launch an impact assessment study to evaluate costs and benefits of different other options," Vestager told the European Parliament.

She made the remarks when asked what rules the EU could adopt to standardize smartphone battery chargers "irrespective of make or model." News of the action was first reported by Reuters.

The EU began taking the voluntary approach to "harmonize" mobile phone charging technology with an agreement that smartphone vendors, including Apple, signed in 2009. In the following years, nearly all smartphone vendors designed their products to work with micro-USB charging — except for Apple, which introduced the Lightning connector in 2012.

This wasn't a violation of the original agreement. The terms offered leeway for Apple to use its propriety Lightning connectors as long as it worked with an adaptor that also supported standard USB connections.

Since the voluntary agreement, and its follow-ups, went into effect, the number of battery charging connectors has declined, limiting electronic waste and cutting down costs for consumers, the EU said in a 2014 study. But on the flip side, iPhone owners have no way to charge their handsets when using their friends' micro-USB cables, unless they possess the right adaptor, the study added.

Apple did not immediately respond to a request for comment.