Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

President Donald Trump has approved a plan to arm the Syrian Kurdish militia — an important U.S. ally in Syria in the fight against ISIS.

The Pentagon said the move is significant because it supports the notion that the Syrian Democratic Force is the fighting force that will eventually go in to Raqqa, a city in Syria's center which has been under ISIS control since 2014. The move also reinforces the idea that the entire Syrian Democratic Force, Syrian Kurds (YPG) and the Syrian Arab Coalition, has the backing of the U.S.

"The (Syrian Democratic Force), partnered with enabling support from U.S. and coalition forces, are the only force on the ground that can successfully seize Raqqa in the near future," chief Pentagon spokesperson Dana White said Tuesday in a statement.

Fighters from the Kurdish People's Protection Units (YPG) stand guard at the site of Turkish airstrikes near northeastern Syrian Kurdish town of Derik, known as al-Malikiyah in Arabic, on April 25, 2017. Delil Souleiman / AFP - Getty Images file

Trump and members of his Cabinet spoke about it during a meeting late Monday at the White House with Secretary of Defense James Mattis joining by video teleconference.

The order has been signed and that “allows the process to begin to function,” one official told NBC News. Once the order comes to the Pentagon, the U.S. can begin providing the Syrian Kurds with arms and equipment fairly quickly since some equipment is pre-positioned.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

The officials could not say what might flow in first or how it would get there, but among the expected options are:

Breaching equipment — bulldozers, engineering equipment

More effective infantry equipment: rifles, ammunition, armor and communication gear (radios)

The officials said the equipment could be delivered by any number of methods: Ground convoys, C-130s, and air drops are all possible, depending on what the equipment is and the area.

It is unclear whether the U.S. may provide bigger equipment.

The news about the U.S. plan to arm Syrian Kurds comes as the The Trump administration mulls sending as many as 5,000 more troops to Afghanistan, a military official told NBC News, and as the White House makes moves it believe will help American forces "start winning" again in the region.

The Turks will be notified about the decision on arming Syrian Kurdish forces soon and the Pentagon expects a strong reaction. In March, Secretary of State Rex Tillerson traveled to Turkey to meet with President Recep Tayyip Erdogan, who sees the YPG as terrorists.

Erdogan is expected to travel to Washington D.C. to meet with the president next week — their first face-to-face meeting since Trump took office — and one in which divisions over U.S. support of the Syrian Kurdish militia are likely to be a point of contention.

In the Syrian conflict, Turkey supports the opposition. However, Turkish forces aren't focused on troops backed by Syria's President Bashar al-Assad — whose leadership is supported by Russia.

Instead, Turkish troops and some Syrian factions have trained their efforts on Syrian Kurds in the country's north as well as ISIS militants.

" We are keenly aware of the security concerns of our coalition partner Turkey," White said in a statement on Tuesday. "We want to reassure the people and government of Turkey that the U.S. is committed to preventing additional security risks and protecting our NATO ally."

Last week, the White House said Trump and Russian President Vladimir Putin discussed by phone ways to resolve the Syria crisis — a six year old civil war which has left more than 500,000 civilians dead, displaced millions and drawn international outrage. That conversation included a "discussion of safe, or de-escalation, zones to achieve lasting peace for humanitarian and many other reasons."