BEIRUT, Lebanon — Syria said Monday that it would agree to allow an Arab mission of military and civilian observers into the country as part of an Arab League proposal to end months of bloodshed there, but it attached a number of conditions, among them the cancellation of economic sanctions decreed by the league.

The Arab League secretary general, Nabil al-Araby, said that he had received a letter from Foreign Minister Walid al-Moallem of Syria detailing the new conditions and that Arab officials were studying them. But he suggested that the offer would provide no breakthrough in the diplomatic dispute between Syria and its Arab brethren over the Syrian conflict, now in its ninth month.

“The conditions contained new elements that we have not heard before,” Mr. Araby told reporters in Cairo. He added that even if Syria agreed to let the monitors in, the league would not immediately revoke its measures. “These sanctions are in force until another decision is adopted by the Arab foreign ministers,” he said.

Since the beginning, Syria has sought to negotiate the league’s proposal to send as many as 500 monitors, conditionally agreeing, but then seeking amendments to a plan that Syrian officials had said would undermine the government’s sovereignty.