South Africa's communications regulator said on Tuesday it was unsure if mobile phone group MTN's proposed tie-up with India's Bharti Airtel would get approval before the end of the year.

I am not too sure (if approval will granted by year-end), Paris Mashile, chairman of the Independent Communications Authority of South Africa (Icasa), told Reuters.

Until such time they bring in all the documentation and facts and everything, we look at it in terms of the licensing conditions of MTN, it is then that we will engage MTN.

The deal, which would create the world's third-largest mobile group by subscribers, is subject to an end-September deadline.

But the two companies have extended talks twice before, and a person with direct knowledge of the matter said on Monday it was possible the talks could be further extended by a few days into October.

MTN and Bharti were involved in similar talks last year but failed to reach an agreement, leading to negotiations being called off.

Bharti has increased the cash component of its offer for a 49 percent stake in MTN to $10 billion from a proposed $7.6 billion, two people familiar with the matter said last week.

On top of that, Bharti would pay $4 billion in stock for a total package of $14 billion, 7 percent more than the earlier $13 billion proposed deal.

(Reporting by Wendell Roelf; Editing by Marius Bosch)