The recent intensification of violence between Israel and the Palestinians is disturbing in many ways. Most disturbing of all are the signs that new weapons technologies and tactics are being transferred to the Palestinian territories, particularly to the Gaza Strip. Tunnels under the Philadelphi corridor along the Egyptian border with Gaza are among the vehicles of arms transfer into Gaza. Reports from Israel about Israeli plans to bomb or reoccupy the Philadelphi corridor to destroy the cross-border tunnels has raised tension in Egypt. Cairo is particularly alarmed because, since the Israeli withdrawal from Gaza little more than a year ago, Egypt has assumed security responsibility in the Philadelphi corridor area. A security breach across the borders between Egypt and Gaza exposes Egyptian-Israeli relations to additional pressure. Insofar as these pressures are security-related this is serious, since security is an area that both Egypt and Israel have hitherto successfully protected from the ups and downs that have characterized their relations in other fields. A unilateral Israeli action in the Philadelphi corridor area is likely to add tension to Egyptian-Israeli relations. It ignores the fact that security along the Egyptian-Israeli-Palestinian borders is a concern for Egypt as well as for Israel. The changing security environment in Sinai is no longer disputed. The terrorist attacks against the main tourist destinations of Taba, Nueiba, Sharm al-Sheikh and Dahab in the past two years have shattered Sinai’s peaceful image. The repeated functional failure of the border control points between Egypt and Gaza in the aftermath of the Israeli withdrawal has caused further concern in Egypt. The tunnels under the Philadelphi corridor are used to smuggle arms and other banned materials and people in both directions. Solid evidence indicates that the rising security threat in Sinai is linked to activities taking place across the Egyptian border with Gaza. Therefore, Egypt and Israel have an equal interest in guarding against the illegal activities taking place in the border area. While coordinating Egyptian-Israeli security policies in the border area might be difficult, coordinated policies should be more sustainable than unilateral actions. Israel and Egypt need to enhance their security cooperation so that they can deal with the changing security environment in the region. Peace in Sinai was the outcome of Egypt’s and Israel’s joint success in managing and resolving their interstate conflict. Current security threats in Sinai are different in quality. It is non-state actors that pose the serious security threats that both Egypt and Israel are now facing. Egyptian terrorist organizations and the support they are likely to be receiving from their counterparts across the border in Gaza are the principal security threat currently directed against Sinai and the border region. Moreover, of all the diverse arrangements between Israel and the Palestinians, arrangements in the Philadelphi corridor have additional, multilateral importance due to Egypt’s involvement. The negotiations that led to these arrangements took place between Egypt and Israel, in the context of the unilateral Israeli withdrawal from the Gaza Strip, while Palestinian involvement was marginal and indirect. Thus, reoccupation of the Philadelphi corridor would be the first explicit violation of a security arrangement between Israel and Egypt. Such a precedent would damage the mutual confidence between Israel and Egypt in a sensitive security field. Further Egyptian involvement in Palestinian-Israeli security arrangements in the future would be less likely, though it might be needed badly. There could be similar consequences regarding other countries, for example Jordan, whose contribution might be needed in future security arrangements. The current controversy regarding a possible unilateral Israeli move in the Philadelphi corridor region is a typical example of the spillover effect of the Palestinian-Israeli conflict. The volatile regional situation provides a conducive environment for that effect to be intensified. Existing security arrangements are far from sufficient to meet the current challenges. The ongoing violence between Palestinian guerrillas and Israel politically restricts the possibility of further Egyptian-Israeli cooperation regarding the security of the border area. Only progress in the political process can facilitate future Israeli-Egyptian cooperation. The revival of the peace process is the answer to many of the current problems in the region, including the problems on the borders between Egypt, Israel and Palestine. Recent developments in Israeli-Palestinian relations offer hope. Thus Israel’s threat to reoccupy the Philadelphi corridor is a serious development. Were it to happen, this would cause a serious setback for efforts to reverse the cycle of violence that has dominated Israeli-Palestinian relations in the year 2006. On the other hand, for a reversal of the course of violence to be consolidated, Egyptian involvement is necessary. Yet winning Egyptian cooperation is unlikely should bombing or reoccupation of the Philadelphi corridor take place. Gamal A. G. Soltan is a senior research fellow at Al-Ahram Center for Political and Strategic Studies in Cairo. This commentary first appeared at bitterlemons-international.org, an online newsletter dealing with Middle Eastern issues.