This reported deal would provide the PSA Group with a 16.3% share in the Europe's small vehicle market, making it the second largest European auto company, ahead of Renault SA, but behind Volkswagen.
Between them, Opel and PSA, which makes Peugeot and Citroen cars, have three factories in Spain, which employ about 13,000 people in total. Spokespeople for PSA and Opel declined to comment.
Prime Minister Theresa May spoke with the boss of Peugeot SA to discuss the takeover bid, and the UK's business secretary, Greg Clark, has met with the French government and PSA.
GM has been struggling to make money in Europe for years and almost sold a majority stake the unit in 2009.
Also on Monday, a morning meeting of Opel workers has been arranged, possibly to announce that the arrangement with PSA would be going ahead.
Last week the BBC learned that both PSA and GM were keen to sign a so-called "statement of intent" before the Geneva Motor Show which starts on 6 March to prevent ongoing speculation overshadowing the release of new models.
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After all, Snap's shareholders will still retain one lever of control: "Investors can vote with their feet", Feldman says. Despite a almost 7-fold increase in revenue, the Los Angeles-based company's net loss jumped 38 percent previous year .
The exact details of the agreement are unknown at this time, but the two sides reportedly made progress on Opel's pension plan, which was underfunded by about $9 billion.
The news site says its two sources familiar with negotiations have confirmed that PSA has agreed to buy Opel from the General, and that the parties plan to make the announcement on Monday.
PSA likely used a non-compete clause to help convince GM to pay more into the pension. Furthermore, French sources have claimed that the acquisition of Opel can offer the group savings of up to €2 billion (around $2.1 billion).
PSA chairman Carlos Tavares last month said that he hopes to create a "European vehicle champion" with the combination and pledged to work with governments and unions that are anxious about job cuts.
The article goes on, saying 2016 marks the 16 consecutive year of losses for GM's European devision, making GM's willingness to ditch the brand-over which it has held control for 90 years-not all too surprising.
Tavares also told his board that PSA would redevelop the Opel lineup with its own technologies to achieve rapid savings, according to people with knowledge of the matter.