WASHINGTON, Aug 9 (Reuters) - US lawmakers said on Monday they were blocking US funding for Lebanon's military after a deadly border clash last week between Lebanon and Israel.

Two key Democrats, Representatives Nita Lowey and Howard Berman, announced they were holding up $100 million that has been approved for Lebanon's army but not yet spent. A senior House Republican, Eric Cantor, said future funding should be stopped too, pending an inquiry.

This incident was tragic and entirely avoidable. US assistance is intended to enhance our safety and that of our allies. On August 3, I placed a hold on 2010 assistance to Lebanon in the wake of this outrageous incident, said Lowey, who chairs the House subcommittee on foreign aid.

The State Department said the Obama administration was not planning to re-evaluate its military cooperation with Lebanon. Spokesman P.J. Crowley said officials were not aware of any US equipment being used during the incident.

U.S. military cooperation program with Lebanon is in the interest of both of our countries and regional stability as a whole, Crowley said. The United States has provided more than $720 million in aid to the Lebanese army since 2006.

Two Lebanese soldiers, a Lebanese journalist and a senior Israeli officer were killed in a rare cross-border skirmish on August 3, the worst such violence since a 2006 war between Israel and Iranian-backed Hezbollah guerrillas.

Israel said a Lebanese army sniper opened fire on two Israeli officers as they watched a tree-pruning operation on the Israeli side of a security fence below the UN Blue line.

The Lebanese army said it first fired warning shots, then Israelis fired at their soldiers. Israeli artillery and tank fire followed.

The UN peacekeeping force in south Lebanon said Israeli soldiers were operating within Israeli territory when the firefight broke out.

U.S. lawmakers were leaning toward the Israeli version of events. Representative Ron Klein, another Democrat, said he had written to Secretary of State Hillary Clinton asking her to investigate what happened. Lawmakers could still release the money that has been allocated, but future appropriations are also at risk.

Certainly I am not going to be supporting any further supplying of any kind of military weaponry to Lebanon if in fact they are escalating the conflict between Israel and Lebanon, Klein said.

Cantor said the point of US aid was to build up a Lebanese fighting force that would serve as a check on the power of Hezbollah in Lebanon, but the lines between Hezbollah and the Lebanese military and government had become blurred.

Berman also said he was concerned about the Iranian- and Syrian-backed movement's reported influence on the Lebanese armed forces. (Editing by Alan Elsner)