WASHINGTON (AFP) - US President Barack Obama has extended sanctions against Syrian or pro-Syrian personalities for provoking instability in neighbouring Lebanon, despite some positive recent signs from Damascus, the White House said. In the past six months, the US has used dialogue with the Syrian government to address concerns and identify areas of mutual interest, including support for Lebanese sovereignty, Obama said in a statement. He said there have been some positive developments in the past year, including the establishment of diplomatic relations and an exchange of ambassadors between Lebanon and Syria. But he said the actions of certain persons continue to contribute to political and economic instability in Lebanon and the region and constitute a continuing unusual and extraordinary threat to the national security and foreign policy of the United States. As a result, he said, he decided to extend for one year sanctions decreed August 1, 2007 by Bush who froze the assets of individuals accused of undermining Lebanons sovereignty on Syrias behalf. The United States has inflicted a whole series of sanctions against Syria, its chief adversary in the region along with Iran, which is allied with Damascus. Since coming to office, Obama has moved cautiously to improve relations with Syria, mindful that it plays or could play an influential role in the region, whether in Lebanon, Iraq or in the Israeli-Palestinian conflict. The Obama administration recently eased trade sanctions against Syria in one recent gesture toward Damascus.