European competition regulators said Tuesday that have stopped the clock in their in-depth investigation into IBM's planned US$745 million takeover of Swedish software maker Telelogic.

The European Commission, Europe's top competition authority, has asked the companies for more information about the deal in order to assess whether it breaks European Union competition rules.

The Commission was due to conclude its investigation by a Feb. 20 deadline. A later date will be set once all the required information has been submitted, a Commission official said, asking not to be named.

The Commission opened a probe of the deal after reaching the preliminary conclusion that the acquisition would cause competition problems. The companies compete head-on in the areas of software modelling and building development tools.

If they join forces this "could have adverse effects on competition," the Commission said.

Telelogic has customers mainly in the aerospace and defense, telecommunications and automotive industries. IBM said when it announced the planned deal that the tie-up would give its clients a wider range of software and system development capabilities.

If the deal is approved, Telelogic will become part of IBM's Rational Software unit.