The U.S. State Department said on Wednesday that the Syrian government is not implementing the peace plan put forward by UN special envoy Kofi Annan, despite the earlier approval of the initiative by the Middle East country.

At a regular briefing, department spokeswoman Victoria Nuland said that Washington made such a conclusion because it has seen "arrests and violence continuing today across Syria from Darra to Hama."

"So it is clear that the Assad regime has not yet taken the necessary steps to implement the commitment that it's made to Kofi Annan," she told reporters.

On Tuesday, a spokesperson for Annan, who is the UN- Arab League joint special envoy for the crisis in Syria, announced that the Syrian government had written to express its acceptance of Annan's plan, which includes proposals for a cease-fire initiated by the Syrian government, a daily halt in fighting for the delivery of humanitarian aid and treatment for the wounded, and talks between the government and the opposition.

Nuland reiterated the position of U.S. State Secretary Hillary Clinton that Syrian President Bashar al-Assad will be judged "by his actions not by his promises."

In light of the upcoming Friends of Syria meeting in Istanbul of Turkey over the weekend and Annan's expected report to the UN Security Council on Monday, she said that it is "incumbent" to keep the pressure on Assad to meet his commitment.

Nuland stressed the need for the Syrian opposition to come up with a united vision at the Istanbul meeting, which, she said, is a focus of this international gathering.