The memorandum of understanding between the US and Iran is not only changing the regional balance of power, but is also shaking up the Lebanese arena.

While Washington seeks to bring an end to the fighting on the northern border and promote regional stability, an internal struggle is underway in Beirut over the image of "the day after," senior security sources say.

The central question is whether Lebanon will exploit the new reality to achieve a full Israeli withdrawal from the south of the country, or will it try to promote a broader security arrangement, which may also change the internal balance of power in it.