The United States told the United Nations on Tuesday it led airstrikes against Islamic State militants in Syria because President Bashar Assad's government had failed to wipe out safe havens used by the group to launch attacks on Iraq.
In a letter to UN Secretary-General Ban Ki-moon, US Ambassador to the United Nations Samantha Power wrote: "The Syrian regime has shown that it cannot and will not confront these safe havens effectively itself."
The strikes were needed to eliminate a threat to Iraq, the United States and its allies, she wrote, citing Article 51 of the UN Charter, which covers an individual or collective right to self-defense against armed attack.
"States must be able to defend themselves ... when, as is the case here, the government of the state where the threat is located is unwilling or unable to prevent the use of its territory for such attacks," Power wrote in the letter obtained by Reuters.
"Accordingly, the United States has initiated necessary and proportionate military actions in Syria in order to eliminate the ongoing (Islamic State) threat to Iraq," she wrote, adding that action was taken also against al Qaeda elements in Syria known as Khorasan "to address terrorist threats that they pose to the United States and our partners and allies."