Turkey has pledged to double the flow of water into the Euphrates river in Iraq over the summer by opening dam floodgates, one of Iraq's vice presidents said on Thursday.

"Vice President Tareq al-Hashemi received this morning a verbal message from the office of Turkish Prime Minister Recep Tayyip Erdogan regarding increasing Iraq's water share," Hashemi's office said.

It said that on Wednesday, Ankara had already increased water flow to Iraq from 360 cubic metres (12,713 cubic feet) per second to 515 m3/second and would ramp that figure up to 715 during July, August and September.

Iraq's water resources minister said last month that Turkey had increased the flow by 130 m3/second. The statement did not say what the levels would be after September.

According to Thursday's statement, Turkey made the promise after requests by Hashemi to Turkish President Abdullah Gul and Erdogan.

"This increase will impact the required irrigation quantity for southern governorates (provinces), and will fulfill shortages in water reserves in both the Haditha dam and Habbaniya reservoirs," it said.

In recent months, Iraq has repeatedly asked Turkey to increase the flow in the Tigris and Euphrates rivers, as a chronic shortage of water for irrigation threatens this year's harvest.

Iraq says Turkey's construction of a series of dams on the rivers' higher reaches has sharply reduced the flow and compounded the problems caused by a nearly decade-long drought.

The flow of on the Euphrates, which runs through Syria before reaching Iraq, is now running at a fraction of its 2000 level of 950 m3/second.

The controversy over the sharing of the mighty rivers at the root of Iraq's ancient name of Mesopotamia -- meaning "between the rivers" in Greek -- is almost as old as the country itself.

But the current dispute comes at an especially sensitive time when a weak and war-devastated Iraq is keen to rekindle diplomatic relations with its more powerful neighbours.