The deal would be signed "in a couple of months (or) it might take a bit longer," Chief Executive Stephen Elop said in a meeting with Finnish journalists. Nokia will adopt Windows Phone software across its smartphones, replacing its home-grown platform, the firms said last week.

Nokia shares dropped more than 20 percent after the strategy turnaround, but industry executives have lauded the new alliance as good for competition and innovation.

Elop said he had sold all his Microsoft shares on Feb. 17 and bought 150,000 shares in Nokia.

Elop started at the helm of Nokia last September and the Canadian is the first non-Finn to head the firm.