WASHINGTON — The Pentagon is pushing back against the notion that there is 'mission creep' in Iraq, as more troops, aircraft and ammunition are deployed to defend against Islamic State of Iraq and the Levant militants.

"There's no mission creep. The missions haven't changed," Pentagon Press Secretary Rear Adm. John Kirby said Tuesday in response to a reporter's question at a press conference. "Some of the numbers have been added in the security-assistance realm ... It's very fluid, and the commander-in-chief and the military leadership here in the building, I think, expect and should have a certain measure of flexibility here in how we ... manage the resources available."

In recent days, the U.S. military sent approximately 300 personnel to reinforce security at the embassy, its support facilities, the Baghdad International Airport and travel routes. The augmented force includes Apache attack helicopters and unarmed drones, according to Kirby. He said the drones will be remotely piloted by personnel at the airport. He did not say how many of either type of aircraft are there.

The U.S. military has already provided nearly 500 air-to-surface Hellfire missiles to the Iraqis this year, according to DOD.

A defense official, speaking on condition of anonymity to discuss future arms sales, said that DOD is working on follow-on sales for a "wide range" of ammunition beyond what the U.S. has already provided.

"It's certainly not going to be the end," according to the official.

The official said that the U.S. intends to sell another 800 Hellfires to the Iraqis for use against ISIL, pending congressional notification.

On Wednesday, Bloomberg News reported that the Obama administration is preparing to sell an additional 4,000 Hellfires to the Iraqi government. But the Pentagon would not confirm whether that sale is in the works.

Kirby said the Defense Department believes that President Barack Obama has authorized the deployment of a sufficient number of troops for the military to accomplish the two missions it has been given: protect American citizens and property, and advise the Iraqi security forces in their fight against ISIL.

Of the 770 troops authorized to be deployed, about 650 are in Iraq now, according to Kirby.

Still, he would not rule out the possibility that more troops and assets will be deployed at some point.

"I won't get ahead of decisions that haven't been made yet about the future in terms of other deployments or other numbers. [But] we believe that the numbers that we've been authorized are sufficient to the tasks we've been given with respect to these two mission areas," Kirby said.

Christopher Harmer, a retired Navy officer who is now a Middle East analyst at the Institute for the Study of War, said that the U.S. military needs to be doing more to change the situation on the ground.

"[The advisers] can impact, but it's not going to be consequential and it's not going to be decisive," he said. "It's almost inevitable that the security situation will require more assistance than the U.S. has currently committed. Whether or not the U.S. decides to give that security assistance is a separate issue."

Harmer said the Iraqi security forces need "all the close air support they can get" from the U.S., but acknowledged that Apaches would be "very vulnerable" to ISIL anti-aircraft weapons if they are flying low.

Kirby was asked why these 300 additional troops and aircraft were being sent into Iraq now.

"The situation has changed on the ground since the 16th of June," when the first wave of extra U.S. forces were deployed to Baghdad to protect diplomatic facilities. "It's not static. It's different every day. And ISIL continues to pose a legitimate threat to Baghdad and its environs, which includes the airport," Kirby said.

But Kirby said it doesn't appear as if ISIL is about to overrun the capital.

"They just continue to put pressure to the north and to the west of Baghdad, but we haven't seen any major advances or anything like that ... It's difficult to tell what their intent is. Clearly they're posing a threat to Baghdad by their sheer presence and their activity and that fact that they are trying to consolidate gains that they have made elsewhere in Iraq. But we haven't seen any overt move, you know, to come in," he said.

Kirby said the Pentagon believes that the Iraqi security forces, aided by Shia militia, will fight to defend the capital if ISIL launches a major assault.