UN Secretary General Ban Ki-moon has called for a "good governance pact" in the Democratic Republic of Congo.
Mr Ban says DR Congo can be an example to Africa
"I would like to invite you to work out a pact with yourselves and the people you represent as well as with all your international partners," Mr Ban said.
He was addressing members of the DRC parliament at the start of a five-day tour of Africa - his first official foreign trip since taking office.
The DRC has the largest deployment of UN soldiers anywhere in the world.
Mr Ban will also join an African Union summit in Ethiopia - the key business part of his trip - and visit Kenya.
He has promised to keep Africa high on his agenda as UN chief.
'Real opposition' needed
The secretary general began his tour in a country still emerging from a bloody civil war.
To loud applause, Mr Ban told the Congolese national assembly the country's elections in 2006 were a real source of hope for Africa - but the task of rebuilding was enormous.
UN PEACEKEEPERS IN AFRICA
DR Congo: 17,000
Sudan: 10,000 in the south, proposal for 20,000 in Darfur, rejected by Sudan govt
Ivory Coast: 9,000
Western Sahara: 200
Somalia: Proposal for UN to take control of 9,000 African Union troops
He said there could be no democracy without justice.
"To be a healthy and thriving democracy [it] needs a real political opposition in which everyone can express himself freely and without fear of being intimidated," Mr Ban told lawmakers.
Calling on the Congolese politicians to co-operate, he said: "This would be a kind of good governance pact, because restoring the state's authority and ensuring the primacy of the rule of law across the country are indispensable for consolidating peace and democracy."
The UN secretary general spoke of the need to re-establish security and urged the creation of "a professional, well-paid and well-equipped army and police as a priority" - and promised continued UN support.
Mr Ban will meet the key opposition leader, Jean-Pierre Bemba and President Joseph Kabila on Sunday.
The UN's theory is that if this vast country can make the transition from war-torn nation to fledgling democracy, it will be a stable influence on the rest of troubled sub-Saharan Africa, says the BBC's UN correspondent, Laura Trevelyan, who is travelling with Mr Ban.
About 17,000 United Nations peacekeepers operate in the country, overseeing the peace process after the end of a bloody five-year war in 2002.
Mr Ban is also due to meet President Omar al-Bashir of Sudan at the AU summit, which opens in the Ethiopian capital, Addis Ababa, on Monday.
Our correspondent says in theory the Sudanese leader has accepted the idea of a joint AU-UN peacekeeping force in the troubled region of Darfur, but it has not happened yet.
The UN chief said the situation in Darfur was "on the top" of his agenda.
"I... am deeply concerned about the continuing violence and the suffering of the civilians there. This time we need action and to make real progress," he said.
He said he would urge President Bashir "to make a clear commitment" to accept the deployment of an UN-AU peacekeeping force in the war-torn region.
Nearly four years of fighting in Darfur has killed some 200,000 people there and more than two million people have been displaced.