(Reuters) -Shares of cloud-based ad tech firm Trade Desk fell by a third during premarket trading on Friday, after CEO Jeff Green warned about ongoing tariff uncertainty pressuring some of the world's largest advertisers.

Trade Desk's stock move looked set to wipe out over $12 billion from the company's market valuation, if losses hold.

Changing trade policies have led to concerns about soft ad spending as companies are holding back on launching new campaigns, particularly in sectors directly affected by tariffs.

Trade Desk, which specializes in helping advertisers buy and optimize digital ad campaigns, has concentrated on large global advertisers.

This focus has made the company more vulnerable to wider economic pressures, in contrast to competitors who rely more on small and medium-sized businesses, Green said on Thursday.

"In an unusual development, TTD decelerated and grew slower than Meta's 22%, which marked an acceleration, prompting worries that closed gardens are growing faster than the open Internet," said Rosenblatt Securities analyst Barton Crockett.

"TTD is also meaningfully exposed to large brands, which are facing tariff pressures."

The company expects the current quarter's revenue to be at least $717 million, largely in line with expectations from analysts compiled by LSEG.

At least seven analysts lowered their price targets on the stock following the results, bringing the median target to $84, as per data compiled by LSEG.

Trade Desk on Thursday also named Alex Kayyal as its chief financial officer, effective August 21, succeeding Laura Schenkein.