Sudan President Omar al-Bashir threatened to overthrow South Sudan's "insect" government, as world powers tried to pull the rivals from the brink of war after the South seized a key oil field.
"Our main target from today is to liberate South Sudan's citizens from the SPLM (Sudan People's Liberation Movement)," Bashir said, adding that the southern regime cannot be called a "movement".
"We call it an insect... trying to destroy Sudan, and our main target from today is to eliminate this insect completely."
Bashir was speaking at a rally Wednesday in support of troops who hope to reclaim Sudan's most important oil field, Heglig, from South Sudanese troops who seized it eight days ago.
"In a few hours you are going to listen to good news from your brothers in Heglig," he told about 3,000 youths, some of them dressed in military gear.
"Heglig will not be the end. The end will be in Juba," the South's capital, said Bashir, whose audience sang songs about jihad, or holy war.
The United Nations, the United States and the European Union have criticised the South's occupation of the oil field, equally denouncing Sudan's air strikes against the South.
There are widespread fears that the fighting will spread.
It is already the worst since South Sudan won independence in July after a 1983-2005 civil war which killed two million people.
"Given the escalation of violence over the past few weeks, given the rhetoric that's being thrown about, we're very concerned," US State Department spokesman Mark Toner told reporters when asked about Bashir's remarks.
Toner repeated Washington's calls for US-supported South Sudan to withdraw from the disputed oil field -- a major base for Sudan's shaky economy -- and for Khartoum to halt air raids.
War debris litters the rust-coloured dirt road into occupied Heglig, where bodies of dead Sudanese soldiers lie scattered. One fell beside a leaking oil facility. Another died in a former Sudanese military compound.
In the face of Bashir's words, South Sudan called for negotiations.
"We can only resolve this through talks with the African Union," South Sudan's Minister of Information, Barnaba Marial Benjamin, told AFP.
While Bashir forecast an imminent victory, a foreign ministry official said Sudan is pursuing both military and diplomatic measures to get South Sudan out of the area.
"We have to end the occupation by hook or crook, by either way," Omar Dahab, head of the ministry's crisis team, told a news conference.
Sudan's military has released virtually no information about the situation on the ground but South Sudan has vowed to hold its positions in Heglig, despite air strikes.
"We thought that we could only resolve this peacefully around a table, but Sudan has been using Heglig as a base to launch attacks on the South," Benjamin said.
Clashes broke out last month in the Heglig area and escalated last week with waves of aerial bombardment hitting the South.
On Tuesday, the UN Security Council discussed possible sanctions against Sudan and South Sudan in a bid to halt a wider war.
Dahab said penalising both would be wrong.
"Logically it should be directed to the aggressor," he said.
Air strikes have killed several South Sudanese civilians and earlier this week damaged a UN peacekeeping camp in the South's Unity State.
The two Sudans are locked "in a logic of war," with hardliners controlling both countries, international peace envoys told the UN Security council.
Although South Sudan disputes it, Heglig has been internationally regarded as being part of Sudan.
Princeton Lyman, the US special envoy on Sudan and South Sudan, was in Khartoum Thursday after a meeting the previous day in the South's capital Juba with President Salva Kiir.
His message will stress "that we need an immediate and unconditional cessation of violence and we need both sides to get back to the AU process," Toner said.
He was referring to talks on a variety of protracted disputes brokered by the African Union. Sudan pulled out of those talks after the Heglig attack.
In another development, the impoverished South Sudan, the world's newest nation, joined the World Bank and the International Monetary Fund on Wednesday.
One of the world's least developed countries, the impoverished African nation achieved independence from Sudan only last July after more than two decades of war.