Alex Henderson said. He added that a deal was unlikely as Nokia lacked the wherewithal and synergies.
Representatives of Nokia, NSN and Juniper declined to comment on the latest report.
Last week, hedge fund Jana Partners disclosed a 2.65 percent stake in Juniper to push the company to cut costs.
Paul Singer's Elliott Management Corp,which owns a 6.2 percent stake in Juniper, has urged the company to buy back shares, start paying a dividend and consider slimming down.
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The hedge fund said the "undervalued" stock could be worth $35-$40 if Juniper implemented its suggestions and focused on revamping its core business of making routers and switches for mobile carriers such as Verizon and AT&T.
"We suspect a merger with Nokia would satisfy the activists if Nokia paid a material premium to Juniper's current $27.20 per share, perhaps valuing Juniper over $35 per share, or a market cap above $17.5 billion,'' Raymond James' Leopold said.
After years of concentrating on cutting costs, NSN has said it is now focussing on expanding the business and competing more aggressively against industry leader Ericsson and China's Huawei.
Other sources have said Nokia has considered a tie-up between NSN and French rival Alcatel-Lucent. Suri has not ruled out acquisitions but has also said the company could grow on its own.