When you or I accept dollars in exchange for providing goods and services, we do so trusting that when we spend those dollars, they will be accepted for an equivalent amount of goods and services.
On this account, governments impose taxes payable only in money, creating a demand for money that means it will be widely accepted as payment for goods.
Lord Triesman welcomed the recent "increased movement" of goods and services in and out of Gaza but accepted it was not enough and a step change was needed.