Libya's Field Marshal Khalifa Haftar has urged his troops to teach unity government forces in Tripoli an "even harder lesson" as Ramadan begins.
Field Marshal Haftar's Libyan National Army launched an assault on April 4 aimed at removing the internationally recognised government from the capital.
That set off another deadly battle in a country mired in violence since the fall of dictator Muammar Qaddafi in 2011.
In a message late on Sunday, Field Marshal Haftar urged his troops to uproot opposing forces from "our beloved country".
"Officers and soldiers of our armed forces and affiliates, I greet you during these glorious days and call on you to inflict on the enemy, with your force and determination, an even harder and bigger lesson than before", he wrote in a message read out by spokesman Gen Ahmed Al Mesmari.
Forces backing the Government of National Accord recently launched a counter-offensive against the LNA, leading to a stalemate on the southern outskirts of the capital.
"In the event of a retreat by the enemy, troops should pursue it with speed and force, prevent it from fleeing and wipe it out," Field Marshal Haftar said.
"Respect the lives of citizens and their goods. Carry out the orders of this letter and those of your superiors."
His message came hours after the UN mission in Libya called for "an extendable, one-week humanitarian truce" starting at 4am on Monday to mark the start of Ramadan.
Also on Sunday, Libya's House of Representatives, the rival government in the east, came a step closer to splintering as 42 dissident politicians selected a "provisional" speaker in opposition to Aguila Saleh, who is aligned with Field Marshal Haftar.
The parliament, elected in 2014, has been based in eastern Libya since it left Tripoli to escape control of militias.
But after Field Marshal Haftar launched his offensive, 42 of its 188 deputies decided to boycott parliamentary activity.
At a second meeting on Sunday, they named Sadeq Al Keheli, their most senior member, as interim speaker for 45 days.
The move was "to provide an opportunity for other lawmakers to join us", rebel deputy Soleiman Al Faqih said.
Mr Al Faqih said that some had been unable to do so because of the security situation in Tripoli.
But the 42 members of parliament fell far short of the quorum of 95 needed for a session to be valid.
While the eastern parliament has won international recognition, it does not extend to a rival administration backed by it and Field Marshal Haftar, in opposition to the Government of National Accord.
But the GNA's status with world powers is increasingly shaky.
US President Donald Trump, in a call with Field Marshal Haftar last month, recognised his "significant role in fighting terrorism and securing Libya's oil resources", the White House said.
Since April 4, fighting between the LNA and forces backing the government in Tripoli has killed at least 432 people, wounded 2,069 and displaced more than 50,000, the UN said.