BEIRUT, Oct 13 (Reuters) - Growing tension over a judicial probe into last year"s Beirut port blast threatens to push Lebanon into yet another political crisis, testing Prime Minister Najib Mikati"s new government as it struggles to dig the country out of economic collapse. More than a year since the explosion ripped through Beirut, killing more than 200 people, Judge Tarek Bitar"s efforts to hold senior officials to account for suspected negligence are facing mounting political pushback, much of it driven by the heavily armed, Iran-backed Shi"ite group Hezbollah. Ministers aligned with the politicians Bitar has sought to question had been expected to press their demand for his removal at a cabinet meeting on Wednesday, after the subject disrupted a stormy session on Tuesday. But Wednesday"s session was postponed until "a framework" could be agreed to tackle the issue, an official source said.A distraction from tackling one of the world"s worst economic depressions, the row risks undermining Mikati, who took office last month after more than a year of squabbling over cabinet seats. It has also underlined the major influence exercised by Hezbollah, which has led calls for Bitar to be replaced, accusing him of conducting a politicised probe. Bitar has not sought to question any Hezbollah members. The most senior politician Bitar wants to question, former finance minister Ali Hassan Khalil, said all options were open for political escalation when asked during an interview on Tuesday whether some ministers could quit. Khalil is the right-hand man of Parliament Speaker Nabih Berri - the most senior Shi"ite in the state - and a close Hezbollah ally. Khalil told al-Mayadeen TV the path of the probe threatened to push Lebanon "towards civil strife". Bitar issued an arrest warrant for Khalil on Tuesday when he failed to show up for questioning. Hezbollah and its Shi"ite ally Amal have pulled their ministers out of government at times of political conflict, a move that would torpedo the Sunni-led cabinet by stripping it of Shi"ite representation. Together with the Christian Marada movement led by Hezbollah ally Suleiman Frangieh, the Shi"ite parties called on supporters to protest against Bitar outside the justice palace on Thursday. Samir Geagea, a Christian opponent of Hezbollah, rejected what he described as any submission to "intimidation" by the group, calling on Lebanese to be ready for peaceful strike action if the "other side" tried to impose its will by force. ENERGY SAPPING Mikati has said Lebanon could not bear the loss of a second judge after the first was removed in February when his impartiality was questioned. Mikati"s priority is reviving IMF talks. But he doesn"t have long, with elections due next spring. Heiko Wimmen of Crisis Group said the row would "sap energy and it also makes (Mikati) look weak". "It puts a huge question mark, or adds one, to the doubts that already everyone has concerning the viability of this government." Hezbollah was "showing its brute influence and force and that definitely reflects badly on Mikati government", added Mohanad Hage Ali of the Carnegie Middle East Center. The government does not have the authority to remove Bitar but could revoke a previous decision that transferred the probe to the judicial council, said Nizar Saghieh, head of the Legal Agenda, a research and advocacy organisation. This would be a major assault on "the separation of powers". Potential foreign aid donors have called for a transparent investigation into the blast, caused by a huge quantity of unsafely stored ammonium nitrate. The U.S. State Department on Tuesday accused Hezbollah of threatening Lebanon"s judiciary. Hezbollah lawmaker Hassan Fadllalah said those remarks violated Lebanese sovereignty and showed "the level of intervention to control the Beirut port blast investigation”. All the senior figures Bitar has sought to question deny wrongdoing, including former prime minister Hassan Diab. The secretariat of parliament said the judiciary had exceeded its powers with any steps against presidents, ministers or MPs. Cases against such officials should go through a special process, Bitar"s critics say.