Iran stopped com­mu­ni­cat­ing with me­di­a­tors af­ter Is­rael threat­ened to bomb Beirut as it fights the Iran­ian-backed Lebanese mili­tia Hezbol­lah, two se­mi-of­fi­cial Iran­ian news agen­cies re­port­ed Tues­day.

Halt­ing com­mu­ni­ca­tion like­ly is a means to fur­ther pres­sure U.S. Pres­i­dent Don­ald Trump over ne­go­ti­a­tions on the cease­fire, which in­clude try­ing to loosen Iran’s choke­hold on the Strait of Hor­muz, through which a fifth of all oil and nat­ur­al gas passed in peace­time. Trump then could po­ten­tial­ly pres­sure Is­raeli Prime Min­is­ter Ben­jamin Ne­tanyahu to halt or slow the ad­vance of his forces, which have moved deep­er in­to Lebanon.

Hezbol­lah re­mains one of Iran’s chief al­lies in its self-de­scribed “ax­is of re­sis­tance” against Is­rael.