The approach of ULIS Article 83 (setting forth a specific interest rate) was rejected by the drafters of the CISG.
CISG Article 78 ULIS Article 83
If a party fails to pay the Where the breach of contract
price or any other sum that consists of delay in the payment
is in arrears, the other of the price, the seller shall in
party is entitled to interest any event be entitled to interest
on it, without prejudice on such sum as is in arrear at a
to any claim for damages rate equal to the official discount
recoverable under rate in the country where he has
article 74. his place of business or, if he
has no place of business,
his habitual residence, plus 1%.