By Ahmed Rasheed

BAGHDAD (Reuters) - Iraqi Prime Minister Nuri al-Maliki flew to Washington on Tuesday, seeking urgent military supplies to fight an upsurge in sectarian violence spilling over the Syrian border.

He will also present himself to President Barack Obama as a potential mediator for him with Iran and Tehran's Syrian ally, Bashar al-Assad, Iraqi sources said - though U.S. officials played down the prospect of Maliki playing such a role.

Two years after his last visit, as U.S. troops were leaving Iraq, Iraq is suffering bombings on a scale not seen since the bloody sectarian chaos of 2006-08. Seeking a third term next year, he also seems to be looking to the shifting diplomatic geometry in the Middle East to help entrench his position.

Speaking at Baghdad airport before flying out for three days of talks in Washington that will culminate at the White House on Friday, Maliki said it was "urgent" that Iraq receive "offensive weapons to combat terrorism and hunt armed groups".

He stressed a need for helicopters and other equipment. Aides have also cited drones as useful for patrolling a border across which the Shi'ite-led government says al Qaeda and other Sunni groups fighting President Assad in Syria are bringing in men and arms that have killed more than 7,000 Iraqis this year.

"We will discuss security and intelligence in addition to arms needed by the military to fight terrorism," said Maliki, who will meet Vice President Joe Biden on Wednesday and Defense Secretary Chuck Hagel with senior U.S. generals on Thursday.

He cited the threat from Syria was high on his agenda and distanced himself from comments by aides who called for faster delivery of F-16 jets, due to arrive in about a year. Such aircraft were not a priority to counter militants, he said.

Maliki's Shi'ite-led government says al Qaeda is bent on securing territory in Iraq, where minority Sunni Muslims are the main community in the desert next to Syria, and wants to destabilize Baghdad to further its goal of ousting Assad.

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However, many Iraqi Sunnis, long dominant until U.S. forces ousted Saddam Hussein in 2003, accuse Maliki of using al Qaeda violence to justify excluding their community from power.

The United States, which fostered the electoral system that put Maliki in office in 2006 at the head of a Shi'ite coalition, has watched with dismay as he has ignored its calls to build consensus and has moved closer to Shi'ite Tehran.

REGIONAL BALANCE

The prime minister, who faced sharp U.S. criticism in March for letting Iran fly weapons and fighters over Iraq to help Assad in Syria, may seek to turn his pivotal position in the region to advantage as the fallout from the Arab uprisings of 2011 and Iran's nuclear program shakes up U.S. strategy.

Maliki made no direct mention of his potential to act as a go-between but several Iraqi officials and politicians told Reuters that he would be discussing that issue in Washington.

"Maliki's message to the Americans is that Iraq is the best broker between Tehran and the West to resolve the nuclear issue," a member of Maliki's State of Law coalition said.

A senior Shi'ite official close to Maliki said: "Everything will be in one basket: Iraq, Iran and Syria."

With the Middle East increasingly divided between a Sunni bloc dominated by Saudi Arabia and Shi'ites looking to non-Arab Iran, Maliki could play a central role - as a Shi'ite Arab leader of a large and central state, who lived for many years in exile in Iran and Syria and has close ties in Washington.

A Shi'ite Iraqi former minister said U.S. officials also saw a closer alliance with Iraq as a possible offset to the estrangement between the United States and Saudi Arabia, which has been angered by Obama's willingness to talk to Iran's new President Hassan Rouhani and his failure to attack Assad.

"America wants Iraq to play a role in solving the Syrian crisis," the former minister said. "The U.S. sees Iraq as a potential balancing point in the Iranian-Saudi conflict."

However, U.S. officials, asked about such statements, said they saw little need for mediation with Iran. One noted that Obama spoke to Rouhani a month ago in the highest-level bilateral contact since 1979 and saw positive developments from the latest nuclear discussions between Tehran and U.N. powers.

"I don't think there is going to be any major pitch," the official said. "It certainly is not going to be the centerpiece of the visit."

Ramzy Mardini at the Iraq Institute for Strategic Studies said Maliki may be promoting himself as a regional player to consolidate his domestic support before an election in April.

"Maliki's road to re-election runs through Washington and Tehran," Mardini said. "There's great political interest to make himself important to both sides, whether the focus is Iran's nuclear program or negotiating a political settlement in Syria. Maliki wants a regional diplomatic role because it most likely assures his third term as prime minister."

(Additional reporting by Suadad al-Salhy in Baghdad, Isabel Coles in Arbil and Arshad Mohammed, Phil Stewart and Andrea Shalal-Esa in Washington; Writing by Alastair Macdonald; Editing by David Stamp)