In this June 5 photo, a man rides a motorcycle in a devastated part of Homs, Syria. Syrian government forces retook the control of Homs in May 2014, after a three year battle with rebels. (Dusan Vranic/AP)

The Obama administration asked Congress on Thursday to authorize $500 million in direct U.S. military training and equipment for Syrian opposition fighters, a move that could significantly escalate U.S. involvement in Syria’s civil war.

Money for the assistance, which would expand a CIA covert training program, is included in a $65.8 billion request for the Pentagon’s Overseas Contingency Operations, or OCO.

The administration has said repeatedly in recent weeks that it was preparing additional assistance to vetted “moderate” opposition forces fighting both the government of Syrian President Bashar al-Assad and extremists of the Islamic State of Iraq and Syria (ISIS), who have now spread their area of control across the Syrian border into Iraq.

If Congress approves the funding, it would mark the first direct U.S. military participation in the Syrian conflict. The training would probably take place in neighboring Jordan, where the CIA is currently training Syrian opposition forces, and possibly in Turkey.

“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 [Assad] regime attacks, push back against the growing number of extremists . . . who find safe-haven in the chaos, and take their future into their own hands by enhancing security and stability at local levels,” National Security Council spokeswoman Caitlin Hayden said in a statement.

The request does not specify the type of military equipment that would be included. Under the existing covert program, the administration has sent limited quantities of small arms and ammunition and has allowed others to send U.S.-made antitank weapons.

But the administration has rebuffed opposition calls for sophisticated weapons, including portable antiaircraft missiles. Placing the training and equipment programs in the hands of the military, rather than the CIA, theoretically will make U.S. aid to the Syrian opposition more transparent.

Although some lawmakers have warned President Obama to stay away from direct involvement in the Syria conflict, many have criticized the administration for dragging its feet on significant aid to the rebels and allowing ISIS and other extremist Sunni Muslim groups to expand across the region.

A strong bipartisan majority of the Senate Armed Services Committee approved language similar to the OCO Syria request during its consideration of the overall Pentagon budget. In initial congressional response to the new request, that panel’s chairman, Carl Levin (D-Mich.), and Rep. Eliot L. Engel (D-N.Y.), a member of the House Foreign Affairs Committee, voiced support.

Details of the OCO budget had been withheld from the administration’s overall fiscal 2015 defense budget request, currently being considered by Congress. The contingency funding also includes money to pay for other counterterrorism operations, increased military deployments in Eastern Europe and for ongoing U.S. expenses in Afghanistan.

The speed with which ISIS forces have virtually eliminated the Syria-Iraq border and taken control of Iraqi cities and towns over the past two weeks has focused the administration’s attention on what now threatens to become a regional conflagration.

Within the OCO request, the Syria money is part of a $5 billion fund announced by Obama last month to help build a new counterterrorism infrastructure with partner countries “from South Asia to the Sahel.”

1 of 9 Full Screen Autoplay Close Skip Ad × Will Syrian war end century-old borders in the Middle East? View Photos Less than 100 years after boundaries were drawn in the Middle East, the durability of those borders — and the nations they formed — is being tested as never before. The sectarian war in Syria is spilling into Iraq, Lebanon, Turkey, Jordan and Israel. Caption Less than 100 years after boundaries were drawn in the Middle East, the durability of those borders — and the nations they formed — is being tested as never before. The sectarian war in Syria is spilling into Iraq, Lebanon, Turkey, Jordan and Israel. July 31, 2013 In Hermel, Lebanon, people cross a bridge over the canal to the Syrian side. Nearly a century ago, Europeans turned up and drew the lines that created the borders of the modern Middle East. But the chaos of Syria’s civil war has muddled the map, creating new frontiers that more closely coincide with the communities they contain. Four flags now fly over the territory known as Syria, representing the competing visions of sect, identity and allegiance that the Syrian war has exposed — and the pieces into which it might break. Dalia Khamissy/For The Washington Post Buy Photo Wait 1 second to continue.

Terrorism, Obama said, remains “the most direct threat to America at home and abroad,” but is no longer centered in an al-Qaeda leadership based in the Afghanistan-Pakistan region. Instead, he said, the threat has become decentralized, with “emerging threats” from al-Qaeda associates and newly formed groups across the Middle East and into Africa.

The Counterterrorism Partnerships Fund, he said, “will allow us to train, build capacity and facilitate partner countries on the front lines.”

A fact sheet released by the White House on Thursday said that $2.5 billion of the new funding would cover the costs of training and operations by both U.S. Special Operations and conventional forces in partner nations, as well as intelligence and surveillance.

An additional $1.5 billion of the fund — about $1 billion of which would be used by the State Department — would be spent on Syria’s neighbors to help improve border security and improve delivery of services to the millions of Syrian refugees now living in Jordan, Lebanon, Turkey and Iraq.

The $500 million training and equipping mission would be aimed at helping “vetted elements” of the Syrian armed opposition to “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.”

Details of the “envisioned” Syria program, the White House said, would be developed “in consultation with the Congress and our international partners.”

The remaining $500 million in the fund would pay for “unforeseen contingencies related to counterterrorism or regional instability,” including the current situation in Iraq, where Obama has increased U.S. surveillance and last week announced he would send up to 300 U.S. military advisers.

A separate $1 billion European Reassurance Initiative would pay for the expanded U.S. military presence in Eastern Europe — including aircraft, troops and pre-positioned equipment — begun in response to Russian aggression in Ukraine.

A substantial portion of the OCO funds are to pay the final withdrawal of U.S. combat troops from Afghanistan by the end of this year, a residual U.S. force of 9,800 troops that Obama has authorized for 2015, and more than $4 billion the United States has agreed to spend annually over the next several years to support Afghan security forces.