Senate President Steve Sweeney has opened a federal exploratory committee with an eye toward a U.S. Senate run, a source with knowledge of Sweeney's plans told PolitickerNJ.

According to the source, Sweeney is eyeing the Senate seat held by U.S. Sen. Frank Lautenberg, but it's unknown if Sweeney plans to challenge the incumbent Democrat in a primary should Lautenberg, who will be 88 later this month, choose to run for another term.  

The source said any discussion of a primary is premature as Lautenberg is not up for re-election until 2014.

Lautenberg has hinted at wanting another term in office, but with two years left in his term has not yet publicly declared his intent.

According to the source, Sweeney has been approached several times over the past two years over a potential run for federal office.

Friday, a spokesman for Lautenberg said the senator will take all comers.

"Senator Lautenberg will be prepared to meet any potential challenge but right now he's focused on working hard for his state and getting Senator Menendez and President Obama re-elected," said spokesman Caley Gray. 

Sweeney is set to begin his second term as Senate President Tuesday abd has served in the upper chamber since 2002.  He is often mentioned on the short list of Democratic candidates who could oppose Gov. Chris Christie in 2013 and the source familiar with his thinking said he is leaving his options open.

Last year, Newark Mayor Cory Booker opened CoryPac, a federal PAC he said he planned to use to help fellow Democrats get elected.  But the PAC gave rise to speculation that Booker plans to run for Lautenberg's seat in 2014.