(CNN) -

The Obama administration says it will seek $500 million from Congress to help "train and equip appropriately vetted elements of the moderate Syrian armed opposition," funding that, if approved, would deepen U.S. involvement in that country's civil war.

National Security Council spokeswoman Caitlin Hayden announced on Thursday that the administration would seek the money that she said would build on "longstanding efforts" by the United States "to empower the moderate Syrian opposition."

"These funds would help defend the Syrian people, stabilize areas under opposition control, facilitate the provision of essential services, counter terrorist threats, and promote conditions for a negotiated settlement," she said.

The $500 million request would be part of a $1.5 billion so-called regional stabilization initiative, which would involve partnering with Jordan, Lebanon, Turkey and Iraq -- Syria's neighbors.

Funding elements of the Syrian opposition would be significant, though it wouldn't necessarily be surprising.

In fact, the U.S. government has been in close contact with some leading the fight to topple President Bashar al-Assad. Last summer, Congress approved some military support for Syrian rebels, and there's been more back-and-forth since then.

Still, any such support is complicated by the fact that the United States doesn't see eye to eye with -- and doesn't want to arm or help in any way -- some elements of the Syrian opposition.

That includes the Islamic State in Iraq and Syria, also known as ISIS or ISIL, a group whose tactics have been so brutal that they've even been disowned by al Qaeda. ISIS, which hopes to establish an Islamic caliphate in the region, is currently making news for taking over a wide swath of Iraq and threatening Baghdad.

Nonetheless, the Obama administration hasn't backed away from other rebels -- seeing them as the best bet, compared to Syria's current government and certain militant fighters.

"While we continue to believe that there is no military solution to this crisis and that the United States should not put American troops into combat in Syria, this request marks another step toward helping the Syrian people defend themselves against regime attacks, push back against the growing number of extremists like ISIL who find safe-haven in the chaos, and take their future into their own hands by enhancing security and stability at local levels," spokeswoman Hayden said.

In May, the President told graduating cadets at the U.S. Military Academy at West Point that he would "work with Congress to ramp up support for those in the Syrian opposition who offer the best alternative to terrorists and a brutal dictator."