(Reuters) - Brazil’s top federal prosecutor will level corruption charges against President Michel Temer one at a time instead of making all the accusations at once, a strategy aimed at weakening his defense, a source with direct knowledge of the process told Reuters on Friday.

President of Brazil Michel Temer speaks during a visit to Norwegian Shipowners Association in Oslo, Norway June 22, 2017. Vidar Ruud/NTB Scanpix/via REUTERS

Under Brazilian law, any criminal charges against a sitting president must be approved by two-thirds of the lower house of Congress in order for the Supreme Court to put a leader on trial.

Top prosecutor Rodrigo Janot is expected to charge Temer with receiving bribes early next week. The president is also facing accusations of racketeering and obstruction of justice.

Temer’s office and his attorney, Antonio Mariz, did not immediately respond to requests for comment. Temer has repeatedly said he is innocent of all accusations.

The investigation is hampering the president’s ability to push his economic reforms through Congress.

Key lawmakers in Temer’s alliance told Reuters this week, on condition of anonymity so they could speak freely, that they will set aside work on those proposed labor law reforms if forced to vote on criminal charges against Temer.

They also said they will not even consider advancing work on pension reforms until changes to the labor law are passed.

Temer is being investigated in connection with a political graft scheme involving JBS SA, the world’s largest meatpacker. Company executives said in plea-bargain testimony that the president took nearly $5 million in bribes in return for help resolving tax matters, for freeing up loans from state-run banks and other matters.

Joesley Batista, one of the brothers who control JBS, also made a recording of a conversation he had with Temer earlier this year. In it the president appears to condone paying off a potential witness. Batista also accused Temer and aides of negotiating millions of dollars in illegal campaign donations for his Brazilian Social Democracy Party.

Lawyers defending Temer were trying to dismiss the use of the recording in the investigation, saying it was manipulated. But police said on Friday after finishing an analysis of the audio files and the equipment used by Joesley Batista to record the president that they were valid.

Lawmakers in Temer’s alliance say they have the one-third of lower-house votes required to block any charges against Temer. Out of 513 deputies, leaders in the alliance said this week they have between 250 and 300 votes.

But they also told Reuters they widely expected Janot to use the strategy of dragging out the charges against Temer in an effort to wear down lawmakers with multiple votes.

Those ballots will be deeply unpopular with Brazilian voters who overwhelmingly believe Temer is corrupt, according to opinion polls.

It also gives more time for possible new corruption revelations to surface against Temer, said another key lawmaker speaking on condition of anonymity, potentially eroding his support in the house.