The Finnish firm said on Monday that it expects to close the deal in April 2014, after previously stating that the sale of its devices and services business to Microsoft would be finished in the first quarter of this year. Analysts believe the group may need to offer further concessions.
Nokia has received regulatory approvals from the European Commission and the U.S. Department of Justice, the company said in a statement on Monday, but approvals from certain antitrust authorities in Asia are still pending.
Microsoft said in an official blog post that the technology giant is "nearing the final stages of our global regulatory approval process".
(Read more: Nokia, Microsoft attempt to rain on Apple's parade)