Nasdaq already owns about 29% of the LSE

The group had set midnight on Friday as the closing date for its offer, but that has now been extended until 1pm UK time on Saturday, 10 February.

However the US market has said it will not raise its 1,243p per share offer.

Nasdaq has blamed the LSE's refusal to enter takeover talks for its decision not to raise its bid price.

The London exchange has consistently rebuffed the offer, dubbing it "wholly inadequate" and has urged shareholders not to sell up.

Meanwhile, the LSE last week issued an upbeat trading forecast and said it would return an extra �250m to shareholders.

On Friday Nasdaq said LSE shareholders had pledged only 0.62% of ordinary, or common, shares, far from reaching the 21% needed to complete its hostile �2.7bn($5.3bn) takeover.

In a statement it said: "LSE shareholders are urged to accept the final offers as you, rather than the LSE board, will determine whether the final offers will be implemented."

Nasdaq must get acceptances from just over 50% of LSE's shareholders - which would include its own 29.37% stake - to complete the takeover.

"This very low level of acceptances is in line with the board's view that Nasdaq's offer substantially undervalues the exchange and fails to reflect its unique strategic position, outstanding financial performance and excellent prospects," the LSE said in a statement.