Singapore Telecommunications Ltd. has begun a strategic review of some businesses after saying it will book a charge of S$1.21 billion ($907.1 million) in its upcoming annual results.

The review will focus on reinvigorating core business, new growth engines, reallocation of capital and unlocking of value, Yuen Kuan Moon, Singtel’s group chief executive officer, said at a media briefing. Some of the digital businesses have taken longer than expected to scale up, he added.

Southeast Asia’s biggest telecom operator has written down impairment charges against its investments in advertising platform Amobee and cybersecurity company Trustwave and sees both companies needing a longer cycle to achieve their goals, it said in a statement issued before the briefing. The company’s Australian unit, Optus, has also undertaken a review and will book similar charges.