European Union states reached a tentative deal Monday to tighten regulation of derivatives markets that sets finance ministers on a collision course with the European Parliament, opening the prospect of months of haggling over a compromise deal.

The rules, known as the Markets in Financial Instruments Directive II, or Mifid II, aim to create a regulated trading environment for over-the-counter derivatives and boost competition among clearing houses in the EU. They are part of an effort by nations of the Group of 20 large economies to shine a light on the more opaque parts of the financial system.