Syrian Government and Rebel Group Agree to Partial Cease-Fire

BEIRUT, Lebanon — The Syrian government and a major opposition group said on Tuesday that they will observe a conditional pause in fighting set to begin Saturday, but they also made clear that they expected the exercise to make little difference in the civil war.

The doubts expressed on all sides — and the volatile state of the battlefield — underscored why even the plan’s sponsors, the United States and Russia, have played down expectations ahead of the partial “cessation of hostilities.”