BRASÍLIA—The Brazilian government unveiled Tuesday a package of infrastructure projects it wants private-sector firms to build and operate, promising a more market-friendly approach than it used in the past.

The package includes roads, railways, ports and airports at an estimated total cost of 198.4 billion Brazilian reais ($64.1 billion). Part of that value reflects planned investment in already existing infrastructure, but the bulk of it is for new projects, Planning Minister Nelson Barbosa said.

All new projects will start no later than 2018, and aim at improving the country’s productivity, he said, adding that some roads could be auctioned as soon as this year and that the plan is important to restore economic growth.

“It is crucial to increase productivity” to achieve “sustainable growth with fiscal stability and lower inflation,” Mr. Barbosa said.

The minister said that the government will use market-friendly procedures to calculate the return rate on projects such as roads, where concessions will go to bidders that offer the lowest toll rate.

But the promise of a market-friendly approach is being met with skepticism. “When details come out, then we will see,” said Josh Duitz, a portfolio manager at Alpine Funds’ Global Infrastructure Fund, who oversees $1.6 billion in investments, including in Brazil. “This government has not been market-friendly and I don’t see that changing yet.”

The planned concessions will also feature reduced subsidized funding from the National Social and Economic Development Bank, or BNDES, officials said. The bank will still be allowed to finance as much as 70% of any project, as it did in the past, but will use its subsidized TJLP interest rate only on 15% of the total loan for airport concessions, 25% for ports and 35% for roads.

Railways are a priority in the government plan, and for them the BNDES can use the subsidized rate for the entire loan.

The government also wants to incentivize bidders to issue bonds in local currency, an underdeveloped market in Brazil. If they do, they would be eligible for extra subsidized financing from the development bank.

Brazil, a major commodities producer, relies on roads to haul much of its soybeans, cotton, coffee and other goods by truck. The roads, seemingly in a perpetual state of disrepair, lead to undersized ports, and produce can often be seen spilled along the route. At the ports, ships and trucks often spend days waiting in line to load or unload.

“Infrastructure is the big bottleneck to improve Brazil’s productivity,” said Clemens Nunes, an economics professor at Fundação Getúlio Vargas college in São Paulo. “You just need to fly over the Santos seaport to see hundreds of ships waiting in line” because the port can’t handle them fast enough, he said.

Fixing the problem has become a priority as the government battles an economic contraction that will likely be more than 1% this year, according to several forecasts. In the past few years, Brasília has tried to spur growth by throwing taxpayer money into the economy, but activity remained sluggish while public debt expanded to 62% of GDP from 52% in 2011, when President Dilma Rousseff was first sworn in.

After winning re-election last year, the president reversed her stimulus policies, naming conservative, cost-cutting economist Joaquim Levy as finance minister.

Together Messrs. Barbosa and Levy unleashed an effort to cut spending and raise taxes to avoid a credit downgrade that could cause a selloff of Brazilian assets and steep currency devaluation. At the same time, the central bank is raising interest rates to tame rampant inflation.

Mr. Barbosa said that the infrastructure plan could help Brazil grow at a 3% annual rate. He said the investment rate in the economy is now less than 20% of gross domestic product, and that the goal is to reach 21% by 2018. The end result, he said, would be faster growth rates with lower inflation.

The success of the concession plan is complicated by the fact that many of Brazil’s largest contractors are engulfed in a corruption scandal around state-controlled oil major Petróleo Brasileiro SA, or Petrobras. Prosecutors say that builders paid bribes to get overpriced contracts with Petrobras. The case is ongoing, but the accused companies may be barred from bidding for new projects.

Mr. Barbosa said that hiring builders is a decision to be made by successful bidders, and that they will be able to hire foreign companies as well.

The government has been trying to lure foreign companies to participate in the new auctions, according to several officials. Last month Chinese prime-minister Li Keqiang visited Brasília and signaled that companies from China may bid for upcoming infrastructure projects in Brazil. Brazilian officials have also said that Ms. Rousseff’s planned visit to the U.S. later this month will help convince American companies to bid.

Mr. Barbosa said that the BNDES is considering offering a line of credit to compensate operators for delays caused by Brazil’s infamous red tape. Under still-undefined circumstances, once a project is stopped because some government body is taking too long to issue a permit, for example, the operator could tap a line of credit that would carry below-market rates, but not so low as to “to incentivize the occurrence,” the minister said.

Corrections & Amplifications

An earlier version of this article misstated details on the BNDES financing of projects. BNDES will no longer use subsidized rates on the entirety of its financing for any project. The use of subsidized rates will also be restricted to 25% of a project’s total cost in some cases.