CAIRO — A nationwide strike by public-sector workers on Thursday threatened to deepen Tunisia’s political and economic crisis in the most visible challenge yet to President Kais Saied’s increasingly authoritarian campaign to concentrate more power in his own hands and right the country’s tottering economy.
Buses, trains, airports, government offices and public companies came to a halt as hundreds of thousands of workers went idle, called off the job by the powerful Tunisian General Labor Union, which represents more than a million workers. UGTT, as the union is known, hopes to thwart the painful subsidy and wage cuts that Mr. Saied’s government is planning to help it secure a loan from the International Monetary Fund.
That lifeline is badly needed, with the price of bread and other basic groceries soaring in the aftermath of Russia’s invasion of Ukraine and Tunisians enduring widespread poverty and unemployment.
The union has also become Mr. Saied’s most powerful antagonist over his political plans, which critics, analysts and Western officials warn run the risk of dismantling Tunisia’s fledgling democracy — the only one to emerge from the Arab Spring protests that swept the region a decade ago.
Since suspending Parliament 11 months ago in response to what he said was the country’s corruption and political dysfunction, Mr. Saied has increased the powers of the presidency — ruling by decree, seizing control of the formerly independent judicial and electoral bodies and marginalizing political parties.
Now, he plans to rewrite the Constitution through a referendum and a national dialogue with various political factions. The new charter is expected to give the presidency even greater powers.
Under pressure from international donors and Western countries to be more inclusive, Mr. Saied has invited a number of political players, including some critics, to participate in the dialogue. But many of them have vowed to boycott the process, among them political parties that at first supported his power grab, law professors he commissioned to redraft the national charter and, perhaps most importantly, UGTT.
The union’s assistant secretary general, Sami Tahiri, has described the plan for the constitutional referendum as a “democratic crime and a global scandal.”
The union backed Mr. Saied’s moves last year, only to turn on him when it found itself shut out of his deliberations in the months afterward.
“We don’t see that this dialogue is bringing any solution to the current situation of the country,” the union’s secretary general, Noureddine Taboubi, told a rally in the capital, Tunis, on Thursday.
He said he was not completely opposed to economic reforms that will be required to get the I.M.F. loan, though he called on the government to help workers cope with inflation by raising wages rather than freezing them, as it has proposed.
“But we want the government to stop its lies,” he added, accusing it of reneging on previous commitments to the union.
A last-ditch negotiating session between the union and the government this week failed to head off the strike.
Mr. Taboubi said that more than 96 percent of his membership had joined the strike across 159 state-run companies and public institutions, though analysts cast doubt on that figure, saying at least one major public company was open on Thursday.
UGTT has insisted it is striking not for political reasons, but to push the government to cushion Tunisian workers from the wage and subsidy cuts the I.M.F. has requested, which the fund has said the government should persuade the union to endorse.
For Mr. Saied, economic health is tied to political ambition, and the union’s opposition to one could endanger the other. Without UGTT’s buy-in on an I.M.F. deal, there may be no loan to stabilize the economy. Without economic stability, public anger could boil over, stripping Mr. Saied of the legitimacy he needs to push through his agenda.
Economic stagnation, corruption and a lack of decent jobs in Tunisia helped ignite the uprising that topped Tunisia’s dictator more than a decade ago. It then contributed to widespread disillusionment with the democratically elected governments that followed, giving Mr. Saied an opening to seize power last year.
Yet he, too, has failed to solve the country’s economic problems, focusing instead on his political ambitions.
In addition to the I.M.F. negotiations, which could offer one way out of the crisis, the president also spoke with his counterpart in the United Arab Emirates this week, hoping to secure investment from the oil-rich regional power.
Even as public confidence in him wanes, however, Mr. Saied can count on one thing: Polls show Tunisians still trust him over the political elites they blame for the last decade’s dysfunction.
That may be true of the union’s leadership as well, said Tarek Kahlaoui, a Tunisian political analyst.
The strike “didn’t get huge support from the population,” he said, noting that it did not spark street demonstrations or other expressions of solidarity.
“UGTT failed to turn their strike into a political protest. From that side, nothing really major happened.”
Still, chaos in Tunisia seems likely to intensify as opposition to Mr. Saied grows without coalescing around a clear alternative to his rule.
Thursday’s strike came during the second week of a strike by Tunisia’s judges, who walked out in protest after Mr. Saied fired 57 judges in early June, accusing them of corruption. The dismissals came soon after Mr. Saied ousted the leadership of the country’s judicial oversight authority and replaced it with his own picks, a move the judges’ association said had erased the authority’s independence.
He did much the same to the electoral commission, which is responsible for running the constitutional referendum in July, raising fears about the integrity of the vote.
Tunisian authorities also recently arrested a journalist for saying in a television interview that the army had refused an order to close UGTT’s office. The government has used military courts to prosecute several civilian critics of Mr. Saied, including members of Parliament and bloggers.
In interviews, several Tunisian workers who went on strike on Thursday said they planned to boycott the constitutional referendum on July 25 because the political process had excluded many factions.
But many said they were simply desperate to stave off the government’s austerity proposals.
“In the past, we were able to make it to the end of the month in terms of expenses. But today, I’m not capable of doing that anymore,” said Dridi Chaouki, a father of three who works for the National Office of Family and Population. “I find myself forced to ask friends to lend me money, just so I can feed my family.”
Massinissa Benlakehalcontributed reporting from Tunis.
