Defense Minister Nelson Jobim will resign, or be fired, once he returns from a trip to the Amazon, the source told Reuters on condition of anonymity. That might not happen until late Thursday or on Friday.

Jobim would be the third minister to lose his job because of clashes with Rousseff or corruption allegations. The turnover has strained relations among members of Rousseff’s 15-party coalition and contributed to the paralysis of economic reforms in Congress.

Jobim had reportedly been unhappy in his job virtually from the moment he agreed to continue as defense minister under Rousseff. He was one of several top officials who also served under her predecessor, Luiz Inacio Lula da Silva.

After long keeping the strains behind closed doors, Jobim had become openly subordinate in recent weeks.

First he raised eyebrows in Brasilia by saying at an opposition party event that he was surrounded by “idiots.” Then he said in a TV interview that he had voted for Rousseff’s opponent, Jose Serra, in last year’s election.

The last straw appears to have been a magazine interview, parts of which were leaked on Thursday, in which Jobim reportedly called one minister a “little weakling.”

He also said that Gleisi Hoffmann, who in June took the critical job of chief of staff, “doesn’t even know Brasilia,” Folha de S.Paulo newspaper reported.

Jobim later denied he had criticized Hoffmann and said the report was part of a campaign to undermine him.

Nevertheless, Rousseff grew tired of Jobim’s constant criticism, especially at a moment when she is trying to repair ties with other parties and also deal with possible fallout in Brazil from the global financial crisis, the source said.

“(Rousseff) has no choice but to remove him,” the official told Reuters. “It’s been a bad couple of weeks.”

Officials have told Reuters that Jobim was angry at being overruled on a major defense contract early in Rousseff’s term when she decided to start over the bidding process for a multi-billion dollar Air Force jets tender.

Jobim had favored France’s Dassault, while Rousseff has said Boeing’s F-18 is the best airplane.

Rousseff has generally won praise from Brazilians and political analysts for her economic management since taking office on Jan. 1.

But her inexperience as a politician — she had never previously held elected office — has alienated even some allies who say that she can be gruff with subordinates and too eager to micromanage policy.

Jobim is a member of the PMDB party, which has fought constantly with Rousseff over issues ranging from budget cuts to plum political jobs. Yet his departure seems unlikely to substantially make relations worse, since his problems were seen as separate from those of the party.

Rousseff’s transport minister resigned last month after allegations of systemic corruption under his watch. Rousseff’s top aide, Antonio Palocci, quit as chief of staff in June amid questions over a massive rise in his personal wealth.

All three ministers had deep ties to Lula, raising the prospect that Rousseff is seeking greater political independence from the leader who oversaw Brazil’s booming economy from 2003 to 2010.