US Ambassador Thomas Krajeski has issued a stark call to Syrian President Bashar Al Assad to step down and leave the country.
He described ongoing violence and killing of civilians in Syria as a "humanitarian disaster".
"We have President Bashar Al Assad, whose government is clearly bent on continuing the murders, oppression of its people and refuses to obey international norms and comply with United Nations plan - even after allowing Kofi Annan to visit the country, as the massacres continue," he said.
"It's time for President Al Assad to step down and he should leave the country."
He made the comments as he addressed US foreign policy in the wake of the Arab Spring.
Meanwhile, he said US policies towards Egypt and Tunisia were unlikely to change despite uprisings that resulted in the election of new leaders.
"The election results in governments being formed and their policies set (will see) the US adjust accordingly," said Mr Krajeski.
"I tend to think there will not be dramatic change in US policies in Egypt and Tunisia and we will continue to have strong bilateral relationships."
He said US foreign policy was dictated by what was best for the American people - including when it came to Bahrain.
"It is my responsibility as the Ambassador of the United States in Bahrain to promote and defend the interest and values of American people," he said.
"Obviously, the events last year in the Middle East affected our policy in one way or another. But it's important to consider each country individually - for example it has not been a peaceful political transition in Egypt or Tunisia."
He also feared continuing violence in Libya.
"We have a new government in Libya and there is still possibility of violence as the country is still getting back on its feet," he said.
"It is a country that is not accustomed to self-rule or any form of democracy, so we are seeing their polices and have some reason for hope."