Monday marks the beginning of a critical week for labor negotiations between the United Auto Workers and two of Detroit’s Big Three automakers.

Labor leaders at Ford Motor Co. will convene at 10 a.m. Monday at the UAW-Ford National Programs Center on Jefferson in downtown Detroit to accept or reject a proposed tentative deal that the union and Dearborn automaker agreed to Friday afternoon.

Also this week, the union will meet with its skilled trades workers at General Motors Co. plants to determine why 59.5 percent of those workers voted “no” on the GM contract. In contrast, 58.3 percent of GM production workers voted “yes,” and, overall, 55.4 percent of all workers voted to approve the contract. Ratification of the pending GM deal was delayed Friday because of the skilled trades rejection.

Under the UAW’s constitution, both skilled trades and production workers must ratify the deal separately. Each group has parts of the contract tailored to their classifications.

After the reason for that rejection is determined through employee meetings, the UAW International Executive Board will decide whether to declare the contract ratified, or if they have to go back to the bargaining table on the skilled trades portion.

The UAW can overrule a rejection by skilled trades workers if the union finds they voted against it for reasons other than issues unique to skilled trades.

That happened in 2011, when a majority of skilled trades workers at Chrysler Group LLC (now Fiat Chrysler Automobiles US) voted against a tentative contract, even though a majority of all workers favored it. The UAW International Executive Board determined that skilled trades workers voted the contract down primarily due to economic issues instead of issues unique to skilled trades workers. Then-UAW President Bob King and the board ratified the whole contract because skilled trades can veto a pact based only on their portion, not shared areas such as raises, vacation days and attendance policies.

There is no indication the National Ford Council will reject the proposed Ford deal; at this stage in negotiations for GM and Fiat Chrysler, their own national councils both unanimously voted to send the proposed pacts to rank-and-file for ratification voting. If that pattern holds true, ratification voting at Ford locals across the country will begin later this week.

The Ford deal is the richest among Detroit’s Big Three.

It includes a $10,000 total signing bonus — $8,500 plus a $1,500 advance in profit sharing — and $9 billion in U.S. plant investments, according to two sources familiar with the deal who asked to remain anonymous because details have not been shared with UAW leaders.

The Ford pact also would include $1,750 in additional annual bonuses and would pattern wage increases for veteran workers after the deal ratified by Fiat Chrysler Automobiles workers and the tentative agreement reached between GM and the UAW, according to a source.

Ford’s agreement also includes moving entry-level workers to traditional workers’ health care plans, similar to the GM pact; $70,000 early retirement buyouts based on seniority; and does not change Ford’s profit-sharing formula that pays hourly workers $1 for every $1 million in North America profits.