"We have been informed that children are being used as human shields by the regime, placed in front of tanks, tortured, raped and assassinated.
"Every day dozens and dozens of Syrians are dying at the hands of Bashar al-Assad's regime.
"We have therefore decided to strengthen our efforts to stop this regime of death and blood."
The United States and Russia are embroiled in a furious diplomatic row after both sides accused each other of supplying arms to Syria.
The US Secretary of State has accused Russia of escalating the conflict in Syria and lying about their involvement in the country.
Foreign Secretary William Hague has told MPs in the House of Commons that Syria is "on the edge of civil war."