Israel's Delek Group signed the letter with the National Electric Power Co. of Jordan.
"The estimate scope of the binding agreement [outlined in the letter] is for the supply of an overall amount of 45 billion cubic meters [1.6 trillion cubic feet] over a period of 15 years," the Israeli company said.
Jordan in the past has struggled to find a reliable source of natural gas in part because of downstream problems in Egypt. In February, Jordanian companies Arab Potash and Jordan Bromine secured a total gross quantity of 66 billion cubic feet of natural gas from the Tamar field, also located off the Israeli coast
Leviathan, with an estimated 18 trillion cubic feet of gas, should go onstream in 2016. Much of the reserves from the offshore field are already designated for exports to regional customers.
Tamar is estimated to hold as much as 10 trillion cubic feet of natural gas.
Delek said the letter is not the same as a formal agreement. Gas prices will be pegged to the price of Brent crude oil.