NEW YORK, United States — Snap Inc, owner of the popular messaging app Snapchat, on Thursday set a lower-than-expected valuation for itself amid mounting investor concerns over the company's still unproven business model, slowing metrics and tight founder control.

The company, which filed for an initial public offering earlier this month, was widely expected to be valued at between $20 billion and $25 billion but fell short by targeting a valuation between $19.5 billion and $22.3 billion ahead of its marketing road show, due to start on Monday in London.

Investors have been poring over the filing for Snap's upcoming IPO to assess whether the still-unprofitable company will be the next Facebook Inc, which has figured out how to make money from its social media platform, or if it will be more like Twitter Inc, which is struggling to achieve the same goal.

"I think that the lower proposed valuation reflects feedback from institutional investors that the higher valuation is hard to justify," Jay Ritter, IPO expert and professor at the University of Florida, said.

"The concerns are about Snap, not the IPO market."

With platform-hopping millennials as its prime customer base and constantly evolving competition, the fact that Snapchat's new user growth has already begun to slow concerns investors, sources said, asking not to be named because the deliberations are confidential.

New active user growth was mostly flat in the early part of the last quarter in 2016, according to the IPO filing. Facebook's Instagram, which had 600 million users as of late 2016, has introduced its own form of disappearing video content. On average, Snapchat has 158 million daily users.

"Snap is already demonstrating decelerating growth before they have managed to break even," said Yann Magnan, managing director at Duff & Phelps.

Snap, which generates most of its revenue from advertising, also saw its loss widen to $514.64 million in 2016 from $372.89 million a year earlier. Much of the company's expenses are for hosting fees it pays to cloud computing companies such as Google to use their infrastructure for its data. It will pay Google $2 billion over the next five years to use its cloud computing services.

Investors have also raised concerns overs Snap's first of its kind three-share class structure, which gives no voting rights to new investors. Snaps co-founders Evan Spiegel and Bobby Murphy, will have the right of 10 votes for every share and existing investors will have one vote for each of their shares.

The company's marketing road show will take place in London, New York, Boston and San Francisco. Snap is expecting to price its IPO after the US market closes on March 1, according to a confidential document reviewed by Reuters.

Snap said in a filing on Thursday it expects to raise as much as $3.2 billion from the offering of 200 million Class A shares. The offering is expected to be priced between $14 and $16 per share.

Even at the low end of that expected valuation range, Snap will be the largest tech offering since Alibaba's IPO in 2014, and after last year's paucity of tech listings, its public launch will be closely watched.

Selling shareholders will sell 55 million shares and the remaining will be sold by the company.

Snap will have about 1.16 billion shares outstanding after the offering and list on the New York Stock Exchange under the symbol SNAP.

"Snap is right to be conservative in setting the initial range. They want to avoid setting a range and then price below the range," said Kathleen Smith, principal at Renaissance Capital, which manages IPO-focused exchange-traded funds.

Snap said it expects to use proceeds of about $2.1 billion for general corporate purposes and to acquire businesses, among other things.

Snap, which launched in 2012 with an app that sends disappearing messages, rebranded itself last year as a camera company and started selling $130 video camera glasses.

Morgan Stanley & Co LLC, Goldman Sachs & Co, JP Morgan Securities LLC, Deutsche Bank Securities Inc, Barclays Capital Inc and Credit Suisse Securities (USA) LLC are among the underwriters to the IPO.

By Sruthi SHankar, Lauren Hirsch, Sweta Singh and Liana Baker; editors Saumyadeb Chakrabarty and Meredith Mazzilli.