Israel is lobbying the United States to keep Syria weak and decentralised, including by letting Russia keep its military bases there to counter Turkey's growing influence in the country, four sources familiar with the efforts said.

Turkey's often fraught ties with Israel have come under severe strain during the Gaza war and Israeli officials have told Washington that Syria's new Islamist rulers, who are backed by Ankara, pose a threat to Israel's borders, the sources said.

The lobbying points to a concerted Israeli campaign to influence U.S. policy at a critical juncture for Syria, as the Islamists who ousted Bashar al-Assad try to stabilise the fractured state and get Washington to lift punishing sanctions. Israel communicated its views to top U.S. officials during meetings in Washington in February and subsequent meetings in Israel with U.S. Congressional representatives, three U.S. sources and another person familiar with the contacts said.