SoftBank Group Corp. is nearing a deal to invest US$500 million in Southeast Asian ride-hailing company GrabTaxi Holdings Pte. Ltd., sources with knowledge of the matter told Reuters.

The talks are reportedly in the advanced stages, with the two companies finalizing the terms of the investment. It is unclear which SoftBank unit is making the investment, according to the report.

Grab is seeking to raise about US$1 billion in its latest funding round, which is expected to be completed in a few weeks, the sources added.

The ride-hailing company is likely to reach out to strategic and financial firms to complete the remainder of the funding, which the sources say could be Grab's last major funding round before a potential initial public offering in the coming years.

Toyota Motor Corp. in June announced that it will invest US$1 billion in Grab to expand the latter's range of online-to-offline services in Southeast Asia. The investment is part of the US$2 billion raised by Grab in that funding round.