Paraguay's President-elect Horacio Cartes, a wealthy businessman, has said he would "never put personal interests before the country's".
Mr Cartes, one of Paraguay's richest men, told reporters there would not be conflict of interest as he governed one of South America's poorest nations.
He said it would be "silly" to stay out of the regional economic bloc Mercosur.
Paraguay was suspended from the group after last year's impeachment of the left-wing President Fernando Lugo.
The move followed a land eviction at a farm that led to the deaths of 11 farmers and six police officers.
The incident sparked a nationwide outcry and the opposition declared President Lugo responsible. Mr Lugo was replaced by Vice-President Federico Franco of the Liberal Party in less than 48 hours.
Neighbouring countries recalled their diplomats calling the impeachment a "congressional coup".
'Do everything possible'
But after Sunday's elections, leaders of the other co-founders of Mercosur, Brazil, Argentina and Uruguay, called Mr Cartes to congratulate him and left the doors to the bloc open.
On Monday, Brazil's President Dilma Rousseff said she was ready "to mend bilateral relations and those between Paraguay and Mercosur".
"We will do everything possible to return to Mercosur," the president-elect told reporters, adding that he did not plan to take part in a June meeting, since he will only take office in August.
The millionaire also said he had stepped down from managerial posts and had become just a shareholder of his 25 companies.
Mr Cartes said he relinquished the control of his enterprises, including a bank, Paraguay's largest tobacco company and a variety of agricultural businesses, to his sister, Sarah.
"In our government there won't be anything that isn't in the public interest, and none of my relatives will be in the administration,'' he told a news conference.
Mr Cartes also faces the challenge of fighting high levels of poverty.
He won the election with 45.8% of the votes, defeating his closest rival, the Liberal Efrain Alegre, by nine percentage points.
The result restored the Colorado Party to power after its defeat by the left-wing candidate Fernando Lugo in 2008.
During his campaign, Mr Cartes had to confront accusations of fraud and links with drug trafficking.
On Monday, he dismissed them again, saying that while he had spent time in prison on allegations of fraud in 1989, all charges against him had eventually been dropped.
He also apologised for comments seen as homophobic, such as saying that the legalisation of same-sex marriage made him think of "the end of the world".
"I'm not ashamed of apologising to those who felt offended [by the comments]," he said on Monday.
Fellow Colorado members have described him as "efficient" and determined to give the Colorado Party a "fresh start".
The party, which came to power in 1947, governed Paraguay for 60 years. It played a key part in supporting the military rule of Gen Alfredo Stroessner from 1954 to 1989.