ADP said the New York-based hedge fund had asked earlier this week to extend the August 10 deadline to nominate directors to its.
Hedge fund billionaire Bill Ackman is trying to shake up the management of his latest target, ADP, a New Jersey-based provider of payroll and benefits services.
ADP defended Rodriguez in it statement and said investors have been rewarded with a total return of 202 percent - assuming they reinvested dividends and held on to shares of a unit that was spun off - during his almost six years at the helm.
SV&C's George Sard, Liz Zale and Jared Levy represent ADP.
"Rodriguez has very broad-based investor support and has factually delivered very compelling returns for shareholders so Pershing Square faces an uphill battle in this case", said Bernstein Research analyst Lisa Ellis.
Ackman met with ADP's leadership this week and said he had a new CEO in mind, people familiar with the matter said.
Ackman had previously invested in ADP from 2009 to 2011. He took his bet on drugmaker Valeant all the way to the bottom, more or less, holding on to Pershing Square's stake until March of this year, despite a 2015 price-spiking scandal that drove off other hedge funds. Everyone's done it: "While I am always praising of you as a person and an intellect if I agree to say something it will be supportive of the company and critical of you". Pershing Square's return over the same period is 29 percent, the statement claimed.
In trading Friday, shares of ADP were up 88 cents, or 0.8 percent, to $112.65. It also provides monthly US employment data through its research institute.
It's not the first time Pershing Square has pushed for changes at the company.