GM shares touched a 54-year low last week, and analysts have said the automaker needs to raise capital to shore up its liquidity in order ride out a sharp downturn in U.S. auto sales.
Wagoner said GM's North American management team was working out new plans to cut costs and shore up the embattled automaker's cash position.
"Our ... team continues to develop further action plans to optimize our operating structure under these new market conditions, improve our cash and funding position, and keep our key product and technology investments on track," he said.
The letter marked the first confirmation from Wagoner that GM was working toward the kind of further restructuring and capital-raising program that Wall Street analysts have said it needs.
GM shares rose almost 2 percent in early trade to $10.40.
The shares have fallen 55 percent since early May, when evidence began to build of a further slowdown in U.S. auto sales that has hit pickup trucks and SUVs hardest.
GM's U.S. sales have dropped almost 16 percent this year, compared with a nearly 10 percent drop in industrywide U.S. auto sales.
Wagoner's message was sent to managers on June 27 but did not widely circulate until this week because it corresponded with the automaker's traditional early July break in operations.
In the e-mail, Wagoner encouraged GM employees to focus on ways to conserve cash.
"As simple as it sounds, what helps most is for each of us to stay focused on our jobs, and especially on what each of us can do to conserve and generate cash," Wagoner said. "And just as important, I encourage you to be positive about the future of our enterprise."