The Trump administration is threatening to veto a resolution to extend the UN's long-standing peacekeeping mission in southern Lebanon if its mandate isn't changed, Israeli and U.S. officials tell me.

Why it matters: The U.S. is the main funder of the UN Interim Force in Lebanon (UNIFIL), which has an annual budget of $250 million. The veto threat is a tactical move, and part of a broader effort to put pressure on Iran and its proxy in Lebanon, Hezbollah.

• The resolution will come before the UN Security Council for a vote at the end of this month.
• It comes in the midst of a deep political crisis in Lebanon, following the Beirut port explosion, and with tensions running high between Israel and Hezbollah.
• The U.S. argues that Hezbollah is restricting the access and movements of the UN force, compromising its effectiveness.
• It wants all restrictions on the peacekeepers' movements lifted, along with enhanced reporting to the Security Council when UNIFIL's operations are challenged.

The Trump administration is also demanding the following changes to UNIFIL’s mandate, per Israeli and U.S. officials.

• Cutting the maximum troop presence from 15,000 to 11,000.
• Reducing the mandate's extension period from one year to six months to allow for more modifications as the situation on the ground changes.
• Immediately implementing recommendations from UN Secretary-General António Guterres, who called for more peacekeepers to be moved to the Israel-Lebanon border area and for the force's weapons, technology and vehicles to be upgraded.

The big picture: UNIFIL was established in 1978 following an Israeli invasion of Lebanon, and its mandate was broadened after the 2006 Iran-Hezbollah War.

• Since then, both Israel and the U.S. have supported the force while also criticizing its failure to prevent Hezbollah’s military entrenchment in southern Lebanon, near the border with Israel.
• Israeli and U.S. officials now say that the force is not implementing its mandate, and so troops numbers should be cut.

In the last several weeks, the U.S. has told Security Council members and the countries supplying the bulk of UNIFIL's troops that they will not agree to a technical rollover of UNIFIL's mandate in a vote scheduled for Aug. 31, Israeli and U.S. officials say.

• In conversations with their counterparts, U.S. and Israeli diplomats have cited the discoveries of Hezbollah's cross-border tunnels into Israel, the cutting of a border fence, limitations on the access and movement of UN peacekeepers by Hezbollah, and a recent attempted attack by Hezbollah on an Israeli outpost.
• “Both us and the Americans stress that in the current reality Hezbollah is just too comfortable with UNIFIL, and this is unacceptable," a senior Israeli official tells me.

In the last few days, the permanent members of the council — China, France, Russia, the U.K. and U.S. — held negotiations on the resolution in New York.

• France is the "pen holder" for the UNIFIL resolution, and French officials have been told by U.S. officials — including Secretary of State Mike Pompeo — that they will veto the resolution if their demands aren't met.
• In the event of a veto, UNIFIL’s operations will cease and the force will be disband.

Between the lines: The U.S. and Israel don't actually want that to happen, and also realize that other members are wary of dramatic steps while Lebanon is in crisis. But both the U.S. and Israel think that only a strong veto threat would convince the other members to agree to substantial changes, officials tell me.

• A State Deperment spokesperson says the U.S. wants UNIFIL to "fully implement its mandate, consider and pursue revisions which reinforce success and recognize shortcomings,” a State Department spokesperson told me. "We are deeply concerned about Hizballah's challenges to UNIFIL's freedom of movement and this is unacceptable."

Where things stand: The French are not impressed by the U.S. veto threat.

• “Veto and then what? They will deploy 10,000 marines to replace UNIFIL?" a senior French diplomat told me.
• The diplomat says France is prepared to work with the U.S. on the matter, but won't agree to all of its demands. "I believe the mandate will be renewed before the end of the month without too much trouble," the diplomat said.