President Ahmed al-Shara of Syria has said that his country is negotiating a potential agreement with Israel aimed at decreasing tensions along their shared border and an accord could be reached “within days.”Syria and Israel have officially been enemies for decades. But since the rebels he led toppled the dictator Bashar al-Assad in December of last year, Mr. al-Shara has pursued a more conciliatory approach. Citing self-defense concerns, Israel has occupied territory in southern Syria and carried out hundreds of airstrikes inside the country, including near the presidential palace where Mr. al-Shara works. With U.S. mediation, officials from his government have been talking to the Israelis for months about a possible security agreement for southern Syria. Mr. al-Shara, speaking to researchers and reporters in the capital, Damascus, late on Wednesday, said Syria is tired of conflict after more than 13 years of civil war and was working to ensure peace with its neighbors.