Guterres told the Security Council that more cost-cutting could hamstring the 18,000-strong MONUSCO force in its efforts to prevent a collapse of the vast, mineral-rich African country.
In a 27-page strategic review of MONUSCO, the UN's largest and most expensive mission, Guterres said the force was streamlining operations after the peacekeeping budget was cut.
"I am confident that the changes under way in MONUSCO will yield efficiencies. Yet, member-states should exercise caution in making further cuts to the mission's budget that may compromise its ability to deliver on its core priorities," Guterres wrote.
Under pressure from the United States, the Security Council in March voted to cut 2,000 troops from MONUSCO while a USD 600-million cut to the peacekeeping budget was agreed for this year by all UN member-states.
More From This Section
In his report, Guterres said holding elections would open the door to a further drawdown of forces and eventually the mission's exit after 17 years in the country.
"Yet, unless the Congolese are able to quickly overcome the current political impasse, the mission may never reach that point," he warned.
In his address to the United Nations last month, President Joseph Kabila said he was "most certainly moving towards credible, transparent and peaceful elections" and that a timetable would be announced "soon."
In power since 2001, Kabila officially ended his term in office in December, but he was allowed to remain under the deal reached on December 31 in exchange for guarantees that elections will be held.
There is little prospect that a vote will be held this year however, fueling concerns that tensions will escalate into large-scale violence.