The Manchester United manager is prepared to hold fire until the summer, when the Glazer family will let him dip into the transfer fund they have accumulated.
Reina raid: United boss is lining up a big money move for the Spanish keeper
A £20m move for Reina is expected then, although the club are also monitoring Atletico Madrid's David de Gea, who would cost £17m.
Reina is known to be unsettled at Liverpool, who are well off the pace for a Champions League spot, and Van der Sar, at 40, is coming to the end of his top-flight career.
Rival: Atletico's De Gea is also being monitored by United
United's debts reached £750m before a recent repayment of £249m and they recorded losses of £83.6m in their last accounts.
But the club have cash reserves estimated to be £120m thanks largely to the £80m sale of Cristiano Ronaldo to Real Madrid last year.
That money will diminish as the season goes on but £50m is thought to be set aside for new signings.
Cash reserves: Joel and Avram Glazer have freed up funds for transfers
The Glazers appear to have paid off the highest interest chunk of United's debts, the payment-in-kind (PIK) loans, themselves rather than rely on an outside investor.
Rumours that Qatar International Holdings might have settled them in return for a stake in the club were discounted after the Glazers issued just two extra shares to cover the amount.
They are thought to have paid off the PIK loans by selling some assets, using cash reserves and arranging alternative credit.
But if they secured the new loans against the shares in their holding companies registered in the USA, then there would be a legal requirement for them to reveal the extent of their debt.
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