Morrell said the military has "convincing and irrefutable evidence that Bilal Hussein is a threat to stability and security in Iraq as a link to insurgent activity".
Dave Tomlin, AP's associate general counsel, rejected the claim: "That's what the military has been saying for 19 months, but whenever we ask to see what's so convincing we get back something that isn't convincing at all."
Morrell said an investigative hearing into the case by the court is scheduled to begin on or after November 28.
"Iraq is still under foreign occupation and Iraqis continue to die in great numbers"
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Under Iraq's legal system, an investigative judge reviews the evidence and decides whether it is sufficient to press charges. The case then goes before a panel of three judges for trial.
Hussein, a native of Falluja, began work for the AP in the summer of 2004.
He was detained on April 12, 2006 after marines entered his house in Ramadi to establish a temporary observation post.
Hussein said he was later taken into custody by the marines who also confiscated equipment including a laptop and satellite phone.
Other reports said the marines allegedly found bomb-making materials and a surveillance photograph of a US military installation.
Morrell said Hussein, who was part of an AP photo team that won a Pulitzer Prize in 2005, had previously aroused suspicion because he was often at the scene of insurgent attacks as they occurred.
He said other evidence, which he would not describe, came to light after Hussein's detention.
Fall in attacks
Also on Monday, the US military said overall attacks in Iraq had fallen 55 per cent since nearly 30,000 additional American troops arrived in Iraq by June.
But Major-General Mark P Hertling, the most senior US commander in northern Iraq, said that al-Qaeda cells still operate in all the key cities in the country's north.
|The US military says attacks have fallen by|
55 per cent since its troop 'surge' [AFP]
He said that despite a decline in violence in Iraq, the north had become more violent than other regions as armed groups moved there to avoid military operations elsewhere.
Hertling said fighters have been pushed east to his area from Anbar by the so-called Awakening movement, in which local tribes supported the US-forces against al-Qaeda.
Other groups have been pushed north to his area from the Baghdad region.
Hertling also indicated the number of roadside bombs or "improvised explosive devices" (IEDs) seen in his region had decreased.
Hertling said 1,830 IEDs were placed in his region in June, compared with 900 last month.
Still, the threat posed by IEDs remains a serious problem, retired General Montgomery Meigs, director of the Pentagon's counter-IED organisation, said on Monday.
Meigs said that while the total number of IED attacks has declined markedly in recent months, the proportion of such attacks that result in US casualties has dropped more slowly, indicating fighters have become more proficient at carrying out the attacks.