FISHKHABOUR, Iraq (Reuters) - Kurds on either side of the river Tigris that runs between Syria and Iraq are linked by kinship, a history of oppression and now by fuel lines and boats ferrying food and medical aid across the waters that divide them.
The lifeline thrown by Iraqi Kurdistan to its neighbour extends the influence of Masoud Barzani, the autonomous region's President, over Kurds in Syria as civil war threatens to dismember the country.
For Syrian Kurds the conflict presents an opportunity to win the kind of rights enjoyed by their ethnic kin in Iraq, who live autonomously from Baghdad with their own administration, armed forces and an increasingly independent foreign policy.
"Besides the humanitarian dimension there is a political dimension (to the aid) as well," said historian Jordi Tejel Gorgas, an expert on Syrian Kurds based in Switzerland. "The KRG (Kurdistan regional government) and Barzani, as leader of a de facto Kurdish state, are showing they are committed patriots."
It is not clear what exactly Barzani may hope to gain, but the aid consolidates his involvement with Kurds in Syria, to whom he has already provided political support in preparation for a future power transition.
KRG spokesman Safeen Dizayee denied there was any ulterior or political motive to the aid, calling it an obligation.
Kurdish areas in Syria's northeastern corner have been spared the worst of the fighting between rebels and forces loyal to President Bashar al-Assad, but are nonetheless suffering from severe food and fuel shortages.
On the Iraqi side of the river, white pick-up trucks reverse down to the water's edge and men heave sack after sack of flour, tinned tomatoes and ghee into the hull of a motor boat waiting to speed over to Syria. The Kurdish flag flies overhead.
"They are our brothers and a shared fate binds us together," Barzani was quoted as saying in the bi-monthly newspaper of a Syrian Kurdish party close to his own.
Divided between Syria, Iraq, Turkey and Iran, the Kurdish people number around 25 million and are often described as the world's largest ethnic group without a state of their own.
In Syria, where they make up about 10 percent of the population, Kurds have been systematically discriminated against under Assad and his father before him, who stripped more than 100,000 of their citizenship.
Kurdistan's approach to Syria contrasts sharply with the central government's. Shi'ite Prime Minister Nuri al-Maliki says Iraq's policy is "non-interference" in Syria, but his interests are closely aligned with those of Iran, which backs Assad.
"The central government has not objected so far," said the head of the crossing, Shawkat Berbehari, a framed portrait of Barzani's father Mulla Mustafa hanging on the wall behind him.
The Fishkhabour crossing opened in mid-January and the authorities are constructing a floating bridge over the river to make it easier to traverse.
"We are helping our brothers and sisters in Western Kurdistan," Berbehari said, using the term by which Kurds refer to the area of Syria they lay claim to as part of their rightful homeland: "Greater Kurdistan".
Around one million litres of diesel and a thousand tonnes of flour as well as medical supplies have been donated so far by the KRG in northern Iraq to their fellow Kurds across the river.
Once laden, each boat takes less than a minute to reach the other side.
"We thank God and we thank the president of Kurdistan for this aid which is an ointment for our wounds," said 49-year-old Amin Ahmed, one of tens of thousands of Syrian Kurds who have sought refuge in the autonomous region.
After being unloaded in Syria, the aid is distributed to Kurds and Arabs alike by committees operating under the "Higher Kurdish Council", a body formed last year at Barzani's insistence to unite rival Syrian Kurdish factions.
The dominant Kurdish group on the ground in Syria is the Democratic Union Party (PYD), aligned with the outlawed Kurdistan Workers' Party (PKK), which has fought a 28-year-old insurgency against the Turkish state.
Weaker but more palatable to the international community is the Kurdish National Council (KNC), itself an umbrella for more than a dozen smaller parties, several of which are tied closely to Iraqi Kurdish groups.
Both the PYD and the KNC are wary of the Arab-dominated Syrian opposition, which they see as inherently hostile to their interests, but they differ on how best to capitalise on the civil war.
The KNC has accused the PYD of colluding with Assad in return for him letting the group's supremacy in Syria's Kurdish areas go unchallenged. That serves Assad's interests by unnerving Turkey, which has supported the uprising against him.
The outcome of the Syrian conflict is still highly uncertain, but analysts say Barzani may be looking to strengthen his foothold on the other side of the border.
"All options are open in Syria and since anything is possible, Barzani might have an eye on Upper Jazira," said Gorgas, referring to the territory where Syrian Kurds are concentrated.
But he said any future government in Syria is unlikely to willingly cede much control over an area with one of the country's few oilfields, and nor would Turkey countenance too strong a Kurdish entity on its southern frontier.
Iraqi Kurdish politicians say their main concern is to prevent Syrian Kurds from repeating the mistakes of the 1990s, when Barzani's Kurdistan Democratic Party (KDP) fought a bloody civil war against the Patriotic Union of Kurdistan (PUK) led by Jalal Talabani.
Although they buried the hatchet to form a shared administration, friction between the KDP and PUK remains, and in Syria they back different Kurdish parties within the KNC.
"One might assume that the PUK will try to undermine Barzani's moves in Syria," Gorgas said, noting that those parties associated with Talabani have tended to lean towards the PYD.
A senior Kurdish politician said Barzani's objectives were to ensure Kurdistan's border with Syria was secure and to contain the PYD: "We want to keep them in the tent," he said on condition of anonymity.
The KRG has cultivated close ties with neighbouring Turkey and does not want the PYD to complicate that strategic relationship, analysts say.
"My sense is that there isn't an over-arching strategy. It's more a reactive response to changing events, with a focus on protecting what they have already gained," said Crispin Hawes, director of political risk consultancy Eurasia Group's Middle East and North Africa practice.
"The ambitions are clearly there to expand but the core desire is that nothing gets rolled back."
Editing by Anna Willard