U.S. warns it may act on Syria as onslaught against Ghouta grinds on

Smoke rises from the besieged Eastern Ghouta in Damascus, February 27. REUTERS/ Bassam Khabieh

UNITED NATIONS/AMMAN (Reuters) - U.S. Ambassador to the United Nations Nikki Haley warned on Monday that Washington "remains prepared to act if we must," if the U.N. Security Council fails to act on Syria, as the Syrian army's onslaught in eastern Ghouta continued unabated.

The United States asked the Security Council to demand an immediate 30-day ceasefire in Damascus and rebel-held eastern Ghouta, where Syrian President Bashar al-Assad's forces, backed by Russia and Iran, say they are targeting "terrorist" groups which are shelling the capital.