Israel agreed to test how it might execute a military withdrawal from Lebanon, under a U.S.-brokered agreement between the two countries unveiled on Friday by Secretary of State Marco Rubio.

Speaking at the State Department, Mr. Rubio said the two countries — which committed months ago to the goal of striking a lasting peace and security deal — had struck a new “framework agreement” to that end after several days of meetings.

Tensions have risen between the Trump administration and both countries about whether Lebanon’s fate will be linked to U.S. peace negotiations with Iran. The agreement reached on Friday amounts to a statement by the United States, Israel and Lebanon that they intend to shape Lebanon’s future independent of the U.S.-Iran conflict.

While Mr. Rubio praised the agreement as a “major milestone,” in remarks to reporters he acknowledged that it marks only “the beginning of the beginning” of negotiations between Israel and Lebanon, adding that “there’s a lot of work ahead.”

The challenges of reaching an enduring pact that would be upheld by the various interested parties appeared to compound on Friday, as retaliatory strikes by the United States on Iranian missile and drone sites added to the precarity of a cease-fire between the two countries.

The centerpiece of the agreement between Israel and Lebanon is a plan for Israel’s military to withdraw from a small fraction of occupied territory in southern Lebanon, which is home to the Iran-backed proxy group Hezbollah. Israel is waging its most sustained war in years against the militant group.