Russia will send fighter jets and attack helicopters to Iran, state media says. The move could strengthen ties that already have the US worried.

• Russia is slated to send Iran advanced fighter jet and attack helicopters, reports say.
• Iranian state media says the agreement will strengthen the country's air force.
• The deal comes amid US warnings that Moscow and Tehran are increasing their defense cooperation.

Russia has agreed to send advanced fighter jets and attack helicopters to Iran in a deal that would provide a significant boost to the country's air force, Iranian media reports.