Javier Solana on Saturday met First Vice President Salva Kiir, successor to John Garang who was killed in a helicopter crash three weeks after taking office after the January peace deal.
The Sudanese government urged the EU to push armed groups in Darfur to negotiate a peace to the conflict in the eastern part of the country.
Some analysts had feared Kiir, previously a secessionist, would reject Garang's vision of a unified Sudan, a charge Kiir has denied.
The southern deal enshrines wealth- and power-sharing, democratic transformation and a southern referendum on secession after six years.
"My feelings are very constructive and very positive," Solana said after meeting Kiir.
"The disappearance of Dr Garang ... made things a little bit more difficult in the beginning, but he [Kiir] has committed himself to do it [implementation]."
"He feels himself not only a man from the south ... but also a Sudanese who wants to construct a Sudan which is prosperous and united. And that's the most important thing we had to hear from him," Solana said.
Salva Kiir became first vice presi-
dent after John Garang's death
The EU is among the biggest donors of humanitarian and development aid to Sudan.
Kiir urged the EU to lift a freeze on 45 million euros in Sudanese funds and to accelerate the transfer of the EU's financial pledges.
Solana is there to review the deal's implementation and the separate conflict in the troubled western Darfur region, not covered by the agreement.
He will travel to Darfur to visit one of the camps for the more than 2 million displaced by that conflict. Darfur peace talks have faltered as violence escalated in recent weeks.
The autonomous southern Sudanese government is to be formed this week. On Saturday, a spokesman for the largest southern militia opposed to Kiir's Sudan People's Liberation Movement (SPLM) said it had agreed with the movement to participate in government and form joint military units.
The pro-government South Sudan Defence Forces (SSDF) say they have about 50,000 fighters. They fought the SPLM during more than two decades of civil war in the south.
The war claimed 2 million lives and was fought over the imposition of Sharia (Islamic law) on the mostly Christian or animist south; division of oil wealth; ethnicity and differences in ideology.