Under a revised agreement between the two Saudi companies inked in October, Saudi Aramco will delay fully paying for the $69.1 billion acquisition of a 70% stake in SABIC by four years until September 2025.

As the source, news reports quote documents filed by the oil giant in connection with the newly reconfirmed launch of an initial public offering (ipo) on Riyadh’s Tadawul stock exchange.

Original terms of the deal called for Aramco to pay the Kingdom’s Public Investment Fund (PIF) half the acquisition sum upfront in cash on closing. The rewritten conditions see it paying only a third of the $69.1 billion price tag immediately.

The purchase of the fund’s stake is due to be completed in the first half of 2020, according to the documents.

Along with the purchase sum, last April’s bond prospectus for the ipo foresaw Aramco paying PIF $1 billion in additional costs in the form of loan charges and promissory notes. The  new terms suggest it may pay $3 billion, however.

As yet, Aramco has published scant details of its four-times-delayed ipo – investors are eagerly awaiting the launch prospectus planned to be published this weekend. Sources have told financial journals that the Kingdom aims to sell a 2% to 5% stake and is hoping to generate proceeds of upward of $100 billion.

Despite the flotation, the Saudi government can be expected to remain the dominant shareholder by far with a 95- 98% stake.

Crown Prince Mohammed bin Salman is said to be eyeing a valuation of $2 trillion for Aramco, while analysts place the company’s value at $1.5 trillion or less. Investment firm Bernstein has estimated a “fair value” at $1.2-2.5 trillion.

Some observers said they thought the $2 trillion named by the crown prince ahead of a launch planned for 2017 had created a benchmark that could result in a lower overall valuation, and that bin Salman might walk away from the plans in the event of a lower valuation.