Over the last week, the privately held company's board voted to take the next step on investment interest from SoftBank , the Japanese conglomerate. It is still considering an offer from a consortium led by Shervin Pishevar, an early investor in the company, to buy Uber shares from an existing investor. The board also earlier voted to go forward with a proposal from a coalition led by the Dragoneer Investment Group to buy stock from Uber's existing shareholders.

Uber's board has voted to move forward on proposals by two investment groups to buy shares in the ride-hailing service and is considering a third offer, with any final decision set to affect who gains the upper hand at the company.

The three proposals were described by four people close to the process, who spoke on the condition of anonymity.

The offers — which are mostly focused on buying Uber stock from current shareholders, rather than issuing new shares — are preliminary. At this stage, the investment groups will begin a due diligence process that could eventually lead to formal investment terms.

The offers have emerged at a delicate time for Uber, which currently has no chief executive and is dealing with board and investor infighting. Travis Kalanick, Uber's co-founder and chief executive, stepped down in June under pressure from investors. Since then, various factions of investors, board members and Mr. Kalanick have all battled to advance their own interests at the company.

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Yet even as Uber undergoes leadership troubles, the company — which is largely funded by venture capital and private equity firms — remains an attractive investment because it is the world's biggest ride-hailing service and is growing fast.

Uber itself does not need new money; the company has raised more than $10 billion in debt and equity and has some $5 billion in the bank.

But the board considered the proposals for a variety of reasons. For some of Uber's existing shareholders, selling stock now could help lock in a hefty profit at a time when the company's future is unclear. One of the proposals could also lead to the ouster of one investor whose firm — Benchmark — has an Uber board seat and that some other board members believe is deliberately damaging the company.

One concern has been whether a share sale could end up negatively affecting Uber's valuation, which stands at $68.5 billion and has made the company the most highly valued private start-up in the world.

Two of the three proposals include buying shares at a discount to Uber's valuation, but also provide a face-saving way for the company to maintain its $68.5 billion value. Dragoneer's investment coalition wants to buy out shareholders at a discount to Uber's current valuation, and SoftBank is offering to buy shares at a lower valuation as well. But both groups would also purchase a small amount of new shares at Uber's current valuation to keep the company's value propped up on paper.

The group led by Mr. Pishevar said it would purchase the shares at the current valuation. Whichever deal ultimately gets approved, this would be the first time that Uber has sold a large chunk of shares at a price that was the same on paper as a previous round of financing.

A spokesman for Uber and a spokeswoman for Uber's board declined to comment, as did SoftBank and a spokeswoman for Mr. Pishevar. Dragoneer did not respond to a request for comment.

SoftBank emerged as one of the first to be interested in buying Uber shares. For months, the conglomerate has angled to purchase the shares from existing investors at a discount to the company's current valuation. To let Uber preserve its $68.5 billion valuation on paper, SoftBank agreed to put a small amount of new money into the company at that price.

Uber's board has been wary of the SoftBank proposal because of investments by its founder and chief executive, Masayoshi Son, in the ride-hailing company's rivals in Asia. But Mr. Son and SoftBank could offer Uber strategic help in Southeast Asia, where the service has been spending heavily. The two sides have quietly worked for weeks to test whether there is enough interest from sellers to make a deal work.

More recently, an investor coalition led by Dragoneer, which includes the private equity firm General Atlantic and others, has emerged with a deal that would protect Uber's valuation. The proposal includes a small purchase of new shares at the current valuation, but the bulk of the investment would come through buying out existing shareholders at a discount via a so-called Dutch auction — an auction that begins with a high price that declines until a buyer says yes.

Uber's board voted a little more than a week ago for the Dragoneer deal to move forward.

The deal was complicated by the emergence last week of another investor consortium led by Mr. Pishevar. The group made a straightforward offer to buy Uber shares from an existing investor at the company's $68.5 billion valuation.

But as a condition of the sale, Mr. Pishevar wants to buy out 75 percent of the shares held by Benchmark, one of Uber's earliest and largest investors. That would cause Benchmark to step down from its seat on Uber's board.

Benchmark's relationship with Uber has deteriorated in recent months after the venture capital firm became one of the key players to push for Mr. Kalanick's resignation as C.E.O. Last week, Benchmark also filed a lawsuit against Mr. Kalanick to force him off Uber's board.

In response, Mr. Pishevar on Friday issued a letter to Benchmark demanding that the firm surrender its seat on the Uber board and sell its Uber shares to outside investors. His investment proposal would reduce Benchmark's stake in the company to the point that it would remove itself from Uber's board.

"While I publicly asked you to resign from the Uber board in light of the overall circumstances, I do have tremendous appreciation for your role in helping the company's development in the past," Mr. Pishevar said in a new letter to Benchmark on Saturday, which was obtained by The New York Times.

A spokeswoman for Benchmark did not immediately respond to a request for comment.

But on Twitter last week, Benchmark said that it was "incredibly optimistic about Uber's future," and that it believed the company could someday be worth $100 billion. But Benchmark also said that Uber would have to have the correct chief executive and be accountable to its riders, drivers and employees before it could be "one of the defining companies of our time."