As time ticked away before the closing time for submissions, WPP, the strong favourite to capture Grey, was said to be still mulling over an offer.
The same was true at Havas, where directors of the group were still meeting in Paris with less than three hours to go to the deadline.
The reluctance to commit came as questions arose about whether Grey, led by its chairman, Ed Meyer, was worth the $1 billion price tag placed on it by the US stock market.
Bob Willott, the editor of Marketing Services Financial Intelligence, asked whether Grey's $1.3 billion annual revenue was sustainable under new ownership; whether a poor operating margin of 6.5 per cent could be boosted to a more acceptable 15 per cent and whether clients would resist attempts to improve revenue.
"Some would ask why a buyer must pay for the improvements that the seller has so far failed to produce," Willott said.
WPP's Sir Martin Sorrell was reported to be tabling a $1.3 billion cash and shares offer for Grey.
His offer may be matched by Havas although any bid stands to be opposed by some of its shareholders who are worried about the group increasing its debt.
A major influence on the outcome could be Procter & Gamble, a bedrock Grey client. The company is thought to be unhappy about a bid by the US buyout company Hellman & Friedman which would probably resell Grey within two or three years.