The order to his Libya National Army posted in an audio recording online came as U.N. Secretary-General Antonio Guterres visited the North African country and issued "a very strong appeal ... for all military movements to stop."
Hifter also put at risk upcoming peace talks between Libyan rivals brokered by the U.N. aimed at drawing a roadmap for new elections. The U.N. Security Council scheduled an emergency closed-door meeting Friday afternoon at Britain's request to discuss the unfolding developments.
The 2011 NATO-supported uprising that toppled and later killed longtime dictator Moammar Gadhafi led to chaos in Libya. The country has been split between rival governments in the east and west and an array of militias fighting over power and oil fields.
Hifter is allied with the east-based administration at odds with the U.N.-backed government based in Tripoli. Alongside the two rival administrations, mostly Islamic militias wield considerable influence and control large swathes of territory in the vast North African nation.
Hifter described his forces' move as a "victorious march" to "shake the lands under the feet of the unjust bunch." "We are coming Tripoli, we are coming," he said. Hifter urged his forces to enter the city peacefully and only raise their weapons "in the face of those who seek injustice and prefer confrontation and fighting."
He also urged his forces not to open fire on any civilians or those who are unarmed. "Those who lay down their weapons are safe, and those who raise the white banner are safe," he said. Secretary-General Guterres not only urged a halt to military movements but appealed for "containment, calm" and "military and political and verbal de-escalation — and the recognition that ... there is no military solution for the problems in Libya."
He told a news conference in Tripoli shortly after Hifter announced the Tripoli offensive that a resumption of dialogue is essential, stressing that "the solution must be political." Hifter's message, which was posted on the Facebook page of the army's media office, comes a day after his forces edged closer to Tripoli and took over the town of Gharyan, 50 kilometers (31 miles) from Tripoli without much fighting.
"I am sipping coffee now in Gharyan," Hifter's top aide Abdel-Salam al-Hassi told The Associated Press over the phone. "God willing, we will enter the rest of the cities without clashes." Skirmishes were reported overnight in the mountain district of al-Assabaah, near Gharyan, in which two people — a resident and a militiaman — were killed, according to the media office of Hifter's forces.
The announcement of Hifter's intention to march on Tripoli comes days before the April 14-16 U.N.-brokered conference aimed at bridging the gap among Libya's factions and draw a road map for new elections and end the country's split.
Guterres is scheduled to meet Hifter in Benghazi on Friday and said his message will include that everyone in Libya must recognize the need for a political solution. "And it is clear for me that we absolutely need to avoid the drama of what would be a major confrontation — namely a major confrontation in Tripoli," he said.
When the secretary-general was asked about postponing the national conference he said the U.N. wants to make sure the military movements end and calm is re-established, which will be important for the meetings to be successful.
"It is difficult to have a National Conference in an environment of global confrontation, so it is very important to de-escalate and to have a situation of restraint and calm." Guterres is the second U.N. chief to visit Libya since the 2011 uprising that toppled Gadhafi. Ban Ki-moon visited in October 2014. Libya, the oil-rich North African country, fell in series of civil wars in different towns and cities, where heavily armed militias fought over power and oil.
Hifter's spokesman, Ahmed al-Mesmari, said LNA forces will give the militiamen in control of the capital the option of surrendering or staying home. "You choose between staying home, handing over your weapons, or raising the white banner," he said, addressing the militias in control of Tripoli.
He said there will be no dialogue with the militias, whom he described as "terrorists," adding that the "game is over" and the "rifle, the artillery, and the jet are the ones speaking now." He also vowed to protect the upcoming peace conference saying the military movement is a separate track from politics.
"The army has nothing to do with politics or with political movement by the United Nations," he said. The European Union's mission to Libya on Thursday also expressed concern over "the military buildup underway in Libya and the escalatory rhetoric which seriously risks leading to an uncontrollable confrontation."
Hifter's army has spread its footprint from eastern Libya where it first battled mostly Islamic militias and Islamist groups, starting in 2014. The campaign then extended southward as Hifter's forces took control of key towns and border crossings earlier this year and now is pushing west, toward Tripoli.
Hifter, who is backed by Egypt and Gulf Arab nations such as the United Arab Emirates, has labeled his rivals as "terrorists" and said in more than one occasion that "liberating" Tripoli is his ultimate goal.
Since Gadhafi's ouster and killing, Libya has descended into chaos, with two rival administrations and an array of militias fighting over power and oil fields.
Associated Press writers Maggie Michael in Cairo and Edith M. Lederer at the United Nations contributed to this report.
Press writer Maggie Michael in Cairo contributed to this report.