* U.S. concerned over kidnappings of Syrians in Lebanon
* Lebanese Foreign Minister says cannot "act upon request"
By Oliver Holmes
BEIRUT, March 8 (Reuters) - Lebanon's foreign minister has rebuffed a call by the U.S. ambassador for the Beirut government to protect all Syrians who have fled across the border into Lebanese territory.
The diplomatic spat illustrates Lebanon's difficulties in dealing with the crisis in its neighbour Syria, which once controlled it and still has powerful allies in its government.
U.S. envoy Maura Connelly visited Interior Minister Marwan Charbel on Tuesday and, while noting Lebanon's right and responsibility to secure its borders, urged the authorities to protect "all disarmed Syrians, including members of the (rebel) Free Syrian Army", according to the embassy's website.
She also "reaffirmed the United States' concern for the disappearance and kidnappings of Syrian nationals in Lebanon".
Foreign Minister Adnan Mansour, who is close to the pro-Syrian Amal faction, responded sharply. "Lebanon cannot heed such a request ... Lebanon does not act upon a request, but out of self-interest for the country's security," he said.
Prime Minister Najib Mikati reinforced that rebuke, saying on his website on Wednesday that the cabinet reminds "diplomatic bodies working in Lebanon of the paramount importance of respecting the Vienna Agreement, Lebanese state institutions and laws".
The 1961 Vienna Convention is a treaty that defines a framework for diplomatic relations, obliging diplomats to respect the laws and regulations of host states.
A U.S. embassy spokeswoman said Connelly had not been responding to specific incidents, but that her comments were consistent with the U.S. position on humanitarian law.
Lebanon has been divided over how to respond to the year-long uprising against Syrian President Bashar al-Assad.
Many politicians have worked to contain the tensions, but former Prime Minister Saad al-Hariri raised the temperature this week when he accused Assad of leading a murderous campaign against his people.
More than 7,000 Syrian refugees have fled into northern Lebanon, according to the U.N. refugee agency.
Syrian forces intervened in Lebanon's civil war in 1976 and remained until 2005 when an outcry over the assassination of Lebanese statesman Rafik al-Hariri forced them to withdraw.
At the time some Lebanese politicians accused Syria of being behind the killing of Hariri, father of Saad al-Hariri. A U.N.-backed special tribunal has indicted four members of the Syrian-and Iranian-backed Hezbollah group. Syria and Hezbollah deny any part in the assassination. (Editing by Alistair Lyon)