Dana Boente, acting US attorney for the Eastern District of Virginia, said the government moved to dismiss the charges after concluding that pre-trial rulings would make it too difficult for the government to prove its case.
|Aipac dismissed Rosen, left, and Weissman, in April 2005 when they were under investigation
He also said he was worried that classified information would be disclosed at trial.
"Given the diminished likelihood the government will prevail at trial under the additional intent requirements imposed by the court and the inevitable disclosure of classified information that would occur at any trial in this matter, we have asked the court to dismiss the indictment," Boente said.
Prosecutors say that TS Ellis, the US district judge, had made several legal rulings that would make it almost impossible to obtain a guilty verdict.
It will be up to Ellis to formally dismiss the charges, but it would be highly unlikely that he would refuse the government's request for dismissal.
Patrick Dorton, an Aipac spokesman, said the organisation is "pleased that the justice department has dismissed the charges. This is a great day for Steve Rosen, Keith Weissman and their families".
Aipac dismissed Rosen and Weissman in April 2005, when they were under investigation but had not yet been charged.
The government's decision won praise from the American Jewish Committee (AJC).
"The department of justice has now reaffirmed that the law of the United States protects citizens who engage in the everyday and essential work of political advocacy," David Harris, the AJC executive director, said.
Weissman's lawyer, Baruch Weiss, called the dismissal a "huge victory for the First Amendment" to the US constitution, which guarantees free-speech rights.
If Rosen and Weissman were convicted, Weiss said it would have set a precedent for prosecuting reporters any time they obtained information from government officials that was later deemed too sensitive to be disclosed.
"[Aipac] is pleased that the Justice Department has dismissed the charges. This is a great day for Steve Rosen, Keith Weissman and their families"
Patrick Dorton, Aipac spokesman
Had the trial gone forward as planned on June 2, it could have included testimony from Stephen Hadley, the former White House national security adviser, and other senior George Bush administration officials.
In 2007, Rosen and Weissman secured the right to subpoena the officials.
Lawrence Franklin, a former Pentagon analyst, pleaded guilty to disclosing information to Rosen and Weissman from early 2002 through June 2004.Policy bias
The defence for Rosen and Weissman had argued that US government officials regularly conveyed sensitive, non-public information to the defendants and others at Aipac, with the expectation it would be disclosed to foreign government officials and the news media.
"Given the proximity of pro-Israeli lobbyists to the governmental mechanisms in the United States, [the dismissal] is not actually that surprising"
Will Youmans, lawyer
They maintained that the secrets were not closely held by the US government and that their disclosure did no damage to the country.
Jane Harman, a Democrat, recently denied she sought to intervene in the case in return for help in getting Democrats to appoint her to lead the House of Representatives Intelligence Committee, which she sat on.
Harman was reported to have recorded in a 2005 phonetap aimed at Israeli espionage, claiming she would seek to have charges against the two men reduced.
Harman did not get the post after Democrats won control of congress in 2006 and left the committee shortly afterwards.
Will Youmans, a lawyer and an activist for Palestinian human rights issues, told Al Jazeera: "Given the proximity of pro-Israeli lobbyists to the governmental mechanisms in the United States, the development is not actually that surprising, given the power during the Bush administrations of the neoconservative school of thought.
"Neoconservative thinkers are closely aligned with Likud party officials in Israel.
"However, it is very troubling that there is that much influence in the US government. It probably accounts for why US foreign policy on Israel and Palestine is so biased and one-sided."