(Recasts with Elliott Advisors statement, background)
LONDON, March 23 (Reuters) - GKN shareholder Elliott Advisors said on Friday it backed a 7.8 billion pound ($11.05 billion) bid by Melrose for the British engineer, as the clock ticks down to next week's deadline for investors to decide on the hostile takeover.
Elliott, which said it had an economic interest over 3.4 percent of GKN shares, told GKN's management it did not trust them to deliver the "profound" cultural shift needed to meet new targets while driving through two deals.
Shareholders have until 1200 GMT on Thursday to support the offer from turnaround specialist Melrose or the GKN management plan to split off the group's auto business and combine it with U.S.-based Dana, leaving GKN focused on aerospace parts.
Investors are divided. Columbia Threadneedle, which also has a 3.4 percent holding, threw its weight behind GKN's plan this week, joining top 30 investor Jupiter Asset Management's Steve Davies.
Elliott, which has joined Aviva Investors in backing Melrose, said in a letter to GKN's executives hostile takeover bids often pressed management teams to come up with ideas that in normal circumstances would be disregarded as "pure fantasy".
"GKN's track-record at improving its operating margins has been unimpressive, yet your team nevertheless claims that it can deliver on its most ambitious plan ever, and that a few potentially qualified individuals can extract the company from its torpor to deliver over a 35 percent increase in profitability," Elliott wrote.
It also encouraged other shareholders to back Melrose.
On Friday, Melrose lifted a self-imposed deadline for approval by the U.S. authorities to enable the acquisition to conclude should shareholders back it next week.
Melrose said discussions with the two U.S. agencies -- the Committee on Foreign Investment in the United States (CFIUS) and the Defence Security Service (DSS) -- were constructive and included potential interim mitigation measures.
A mainstay of Britain's engineering sector, GKN makes parts for the U.S. aviation industry, such as the Boeing 737 jet and Black Hawk helicopter, as well as components for Volkswagen and Ford cars.
($1 = 0.7062 pounds)
Reporting by Sarah Young Editing by Keith Weir and Edmund Blair