BBC News with Jonathan Izard.
The US Secretary of State John Kerry has warned US senators before their debate on Syria next week that they must not fail to respond to what he called an undeniable chemical attack by President Assad on his own people. He said standing aside would give the green light to other dictators. But Mr. Kerry said he wanted to make it clear that President Obama's objectives were limited.
He is asking only for the power to make clear, to make certain that the United States means what we say, that the world, when we join together in a multilateral statement, mean what we say. He's asking for authorization to degrade and deter Bashar al-Assad's capacity to use chemical weapons.
The leader of the Republicans in the US House of Representatives John Boehner has said he supports Barack Obama's call for military intervention in Syria, a significant boost for the president.
The UN Secretary General Ban Ki-moon has said that if it is proved that chemical weapons were used in Syria the Security Council has an obligation to act but he added that the use of force would only be legal with UN approval. Nick Bryant reports.
While the UN Secretary General Ban Ki-moon stop short of using the word illegal to describe any possible military action by America against Syria. He said the use of force would only be lawful in self-defense or it backed by the Security Council. If confirmed the use of chemical weapons would mark a serious violation of international law, he said but a military response could unleash more turmoil.