A US administration source revealed on Wednesday that intelligence services in his country are closely monitoring what he described as “suspicious air cargo” between Iran and Syria, suspected of carrying weapons or military systems. Israel and the United States suspect a series of cargo flights from Iran to Syria may be transporting weapons to the head of the Syrian regime, Bashar Assad, and Iranian forces in his country, CNN reported on Wednesday. While weapons shipments into Syria are not uncommon, cargo involving Iran have caught the attention of US intelligence because they occurred in the days after the April 13 US airstrikes on regime targets in the war-torn country.  Rhetoric between Iran and Israel has also escalated in recent weeks over Tehrans involvement in areas of Syria that can be used to potentially launch missiles or aircraft that could target Israel.  Iran is threatening to "respond appropriately sooner or later" to the strike on the Syrian regimes T4 air base near the western city of Homs, an attack which caused Iranian casualties. Iranian reports acknowledged the killing of at least 7 Iranians in the strike.  Moscow and Damascus have confirmed that Israel bombed the airport. Israeli reports have also indicated that Israels northern border is on a state of alert amid fears of a possible response from Iran or its Lebanon-based proxy “Hezbollah.”