Counting down his final weeks in office, Panamanian President Ricardo Martinelli on Saturday is inaugurating the most-emblematic project of a five-year term marked by fast economic growth and more than a hint of hubris — Central America’s first subway system.

The metro will surely alleviate the booming capital’s dreadful traffic. But critics say the $2 billion spent on the 9-mile (14-kilometer) rail line would have been better used building a higher-capacity surface transport network and expanded bus system.

The critics also are unhappy about what they consider Saturday evening’s over-the-top party, with a free concert and fireworks, to celebrate the new subway. They call it a political stunt a month before Panama’s elections to drum up support for Martinelli’s preferred successor, former Housing Minister Jose Domingo Arias.

Trains themselves won’t start running a full schedule until Monday.

Martinelli, who leaves office July 1, isn’t fazed by the criticism. Notably brash with friends and foes alike, the 62-year-old supermarket magnate hasn’t tired of boasting that he has accomplished more in five years than was done in the previous 50. He has an approval rating of 60 percent, and relishes the chance of getting his chosen successor elected, which no incumbent Panamanian president has done since democracy was restored in 1989.

“This is a project that makes the opposition burn,” Roberto Henriquez, a presidential aide, said in a recent television interview. “But gentleman, I’m sorry: The metro is a reality, and next week we’ll be delivering the benefits to all the people.”

Since Martinelli took office in 2009, Panama has spent upward of $15 billion on infrastructure improvements, including new hospitals, airports and 990 miles (1,600 kilometers) of highways. The subway is Panama’s second costliest project in the past century, surpassed only by the current $5.25 billion expansion of the Panama Canal that began before he became president.

“Never has a government done so much for a country and its people,” proclaims a TV ad featuring the subway and a catchy, merengue-tinged chorus of “Promises Fulfilled.”

The government hasn’t announced how much a ride will cost. Instead, it is waiving fares for the first few months in what analysts say is a clear attempt to boost the candidacy of the little-known Arias, who holds a narrow lead in most polls over former Panama City Mayor Juan Carlos Navarro.

Panama’s region-leading infrastructure is a point of pride for many of the country’s 3.4 million people, although the spending hasn’t been without controversy.

Vice President Juan Carlos Varela broke with Martinelli in 2011 and later accused the president and his two sons of taking kickbacks from Italy’s state-controlled Finmeccanica in exchange for government contracts.

No charges were filed against the president, but the allegation has reinforced perceptions that the construction — which has propelled economic growth averaging 9 percent a year since 2010 — is also fueling corruption and waste. Panama fell 20 places to 102nd in Transparency International’s latest annual ranking of 177 countries on corruption.

The subway cost 30 percent more than the price budgeted when the contract to build it was awarded to Brazilian construction giant Odebrecht SA in 2010. Roberto Roy, the metro’s top executive, says costs rose because of design changes, including construction of two additional stations.

Martinelli’s penchant for self-promotion led to the two giant boring machines used to dig the metro’s more than 4 miles (7 kilometers) of tunnels being named Marta and Carolina, in honor of his wife and daughter.

First lady Marta Linares is Arias’ running mate, a sign that Martinelli will remain influential if his political disciple wins. The president was barred by the constitution from seeking re-election.

Carolina Rodriguez, who works as a maid in the downtown district of flashy, high-rise apartment buildings, doesn’t much mind the political overtones of the subway’s inauguration so long as the train reduces her pre-dawn commute and remains affordable.

“It’s all very pretty and Martinelli says the train will help us,” said Rodriguez, who spends 90 minutes every day commuting in from San Miguelito, a poor neighborhood on the subway’s northern terminus. “Hopefully the train will relieve my daily headache.”

Associated Press writer Joshua Goodman in Bogota, Colombia, contributed to this report.