Akobo - South Sudan's opposition is threatening to resort to "guerrilla warfare" if peace talks in Ethiopia fail in the coming days as government forces advance on remaining rebel strongholds in the fifth year of civil war."We will keep fighting from the bush by using insurgencies and tactical strategies," James Otong, general deputy commander for the armed opposition, told The Associated Press during a visit to the rebel-held town of Akobo, near the Ethiopian border.Untold tens of thousands of people have been killed and millions displaced since the world's youngest nation plunged into civil war in late 2013. Although high-level peace talks are set to resume on February 5, opposition forces accuse the government of being more interested in "waging war" than in ending the conflict. The government says it acts only in self-defense.The international community is openly frustrated with both sides as a cease-fire that took effect Dec. 24 was violated within hours. The United States is pressing the UN Security Council to impose an arms embargo on South Sudan, saying its leaders are "betraying" the country.KEEP UPDATED on the latest news from around the continent by subscribing to our FREE newsletter, Hello Africa.FOLLOW News24 Africa on Twitter and Facebook. In Akobo, one of the last opposition strongholds, the AP spoke with several displaced families who said they fled recent attacks by government forces."They're probably dead," Nyakum Well said of her missing children, choking back tears as she sat in her small teashop under a tree. "If [President] Salva Kiir's government captures any human being they kill them."Five days earlier, the 27-year-old was separated from her two young children when government troops attacked her town of Pieri, killing civilians and burning houses, she said.Aid workers in Akobo estimate that 100 people have been flowing in daily since the middle of January. Local authorities are concerned the town will be targeted next.Conflict experts said Akobo is considered the most "strategic and symbolic" of the remaining rebel-held areas and that the government is attempting to walk a "diplomatic tightrope" between advancing militarily and appeasing the international community."The government thinks it is winning the war militarily, so it doesn't see any reason to cede any real power through peace negotiations," said Alan Boswell, the South Sudan analyst for Small Arms Survey, a Geneva-based group focusing on armed violence.Patience fading quickly Even if the rebels continue guerrilla warfare, they lack the resources to threaten the regime or "protect the civilian population from government assaults," Boswell said.In recent months the opposition has ceded critical ground to the government, including the town of Lasu, its headquarters in the Equatoria region. The rebels still control a handful of areas across the country and roam freely in many rural areas, while key towns and the cities are under government control. It is not clear how many rebels are still fighting.South Sudan's army denies claims that it is focused on expanding its territory, saying there's no strategy to intensify the war."We're focused on winning the minds and hearts of our people," army spokesperson Lul Ruai Koang said.Yet the international community's patience is fading quickly."It is long past time for the leaders of South Sudan to get serious and put the interests of the people of South Sudan before their own personal gain," Mark Weinberg, public affairs officer for the U.S. Embassy, told the AP. He said the US and regional bodies will find ways to hold those who "block peace" accountable but didn't elaborate.Agreement A past US attempt under the Obama administration to have a UN arms embargo imposed on South Sudan failed without enough support from Security Council members. On Saturday, UN Secretary-General Antonio Guterres told African regional bodies he didn't think such "tougher measures" can come from the Security Council and that they need to come from the region instead.Speaking ahead of the new round of peace talks, the chairman of the independent Joint Monitoring and Evaluation Commission, Festus Mogae, condemned South Sudan's leaders for signing a cease-fire agreement one day and allowing its "violation with impunity" the next."It is now time to revisit the range of practical measures that can be applied in earnest to those who refuse to take this process seriously," Mogae said.South Sudanese who are weary of the fighting doubt that a solution is in sight when peace talks resume in Ethiopia's capital, Addis Ababa.Sheltering in her makeshift home in one of Akobo's rundown schools, 27-year-old Nyajok Kir said her son was killed one week earlier when government troops stormed her town of Yuai and started indiscriminately shooting civilians."There was an agreement in Addis before," she said, hanging her head. "But [President] Kiir doesn't like the peace."