European Union regulators on Wednesday started analyzing Microsoft Corp.”s proposal to comply with an antitrust ruling involving its Windows platform and will seek advice from the software maker”s rivals before deciding whether to impose additional fines against the company.

If the European Union deems the proposal insufficient, it might slap heavy sanctions on the company of up to 5 percent of its daily global sales.

&#34It will probably take us a few weeks to carry out this analysis,&#34 said EU spokesman Jonathan Todd. &#34We will have to cross-check it with the market participants and look at everything in depth.&#34

Microsoft has to answer complaints from the EU head office that it was not fully complying with last year”s ruling, which imposed a fine of 497 million euros ($624 million) and said Microsoft abusively wielded its Windows software domination to lock competitors out of the market.

Both sides were in contact almost up until midnight Tuesday, the EU-imposed deadline following weeks of negotiations. &#34We received all sorts of documents,&#34 Todd said, but refused to discuss the content of the proposal.

&#34We are awaiting a response from the EU Commission,&#34 said Microsoft spokesman Tom Brookes. Microsoft, too, declined to talk about any aspect of its submitted papers.

Once the Commission has come to a decision on the Microsoft proposal, it will inform the company, which will then have time to rebut. Then the EU member states will be consulted and the full EU executive Commission will decide on the case.

The process will likely last until the end of July.

During the last days of talks, negotiations centered on pricing and royalties that can be charged to allow software competitors to better dovetail their products with Microsoft”s Windows platform.

The orders of the European Commission require Microsoft to share its Windows server code with rivals under certain conditions to make the industry more competitive in the European marketplace.

Last month, the EU”s regulators were still not convinced the Windows version the company was forced to produce without Media Player was up to technical standards.

Microsoft said in the past it would give competitors a price break on reviewing source code and more time to decide whether they wanted to license it.

The fine itself is not part of the disagreements between the two sides.

During the last high-level contacts last month, EU antitrust chief Neelie Kroes held talks with Microsoft CEO Steve Ballmer to seek a breakthrough in the five-year standoff.