The White House said on Friday an agreement for a break in hostilities in the Syrian conflict is significant, but there is still more to be done in the peace talks.
"This was an important step, but the work is far from over," White House spokesman Eric Schultz told reporters in a briefing.
"In the coming days we will be looking for actions, not words, to demonstrate that all parties are prepared to honor their commitments," he said.
Major powers agreed on Friday to begin a cessation of hostilities in Syria in a week, but Russia pressed on with bombing in support of its ally President Bashar Assad, who vowed to fight until he regained full control of the country.
Schultz said Russia had contributed to the humanitarian crisis in Syria in some instances by targeting areas where there was little presence by the militant group Islamic State.
"It is time for them to stop using the cover of going after ISIL to become more involved in the sectarian civil war," he said, using an acronym for Islamic State.