As fighters from the Islamic State of Iraq and Syria move weapons won in their takeover of Mosul and Tikrit over the now open border to Deir Ezzor province, Syrian Kurds are preparing to defend their territory from a potential ISIS advance.

Cross-border cooperation between Kurds could lead to a strengthening of their unity – or autonomy.

Analysts say that if ISIS brings the fight to Kurdish territory, the YPG, the armed wing of the Kurdish northeast’s controlling Kurdish Democratic Union Party, could form a fighting coalition with al Qaida-linked Jabhat al-Nusra, ISIS’s Syrian archrival, as well as the rebel Islamic Front.

They could also align with Iraq’s Kurdistan Democratic Party and the peshmerga, the Iraqi Kurdish militia that has taken control of Rabia, one of the two official border crossings with Syria.

“It wouldn’t surprise me if there was some low-level cooperation between Syrian Kurds and forces belonging to the Kurdish region of Iraq, particularly around the border crossings,” says Thomas McGee, a scholar and researcher focusing on Syrian Kurds. “They’re really trying to present themselves as a good option to the international community [as the choice party] to fight back against ISIS.”

“Certainly over the last couple of years, since the emergence of a separate Kurdish [militant] entity in Syria, we have seen a level of cooperation between Erbil and some elements within the Kurdish administration in Syria,” says Jordan Perry, analyst for the Middle East and North Africa at UK-based Maplecroft, a global risks consultancy.

Already, “the YPG and KDP are acting together in the Mosul area to safeguard the Iraq-Syrian border on the Iraqi side,” says Mutlu Civiroglu, a Washington-based Syrian and Kurdish affairs analyst.

Thus far, however, any collaboration between the two groups has focused on defending the Iraqi side of the border.

“In terms of security, [the Syrians] are working more together with Kurds on the other side of border,” says Wladimir van Wilgenburg, a Kurdish analyst at the Jamestown Institute.

In the Syrian Kurdish cities of Afrin and Kobani, van Wilgenburg says anti-ISIS help is coming not from Iraq, but from another neighbor. “Kurds are coming from Turkey and they’re going to fight against ISIS. At the moment, they’re still trying to work with more moderate rebel groups in coastal Raqqa.”

The main concern for Syria’s Kurds is an ISIS advance further into eastern Deir Ezzor province, then into Hassakeh, the Kurdish territory where its fighters have been battling the YPG for more than two years. They have had more success in fighting ISIS than the Free Syrian Army, Jabhat al-Nusra or even the Syrian regime.

“The way things seem to be going regionally, coalitions are becoming more concrete talking points. The sentiment on the Kurdish street is that Kurds should all band together,” McGee says.

“Some officials from the PYD went to Iraqi Kurdistan to meet them, and some high level PYD officials are now in Istanbul. It’s one of first times they’ve been there. These trips are leading people to all kinds of conclusions that there’s going to be some ‘super coalition’ of the Kurds against ISIS. We’ve seen this already in some areas of Iraqi Kurdistan – some of the groups who had bad relations with the PYD [before this] are banding together with them against ISIS.”

Major problems between ISIS and the Kurds generally only arise in areas where Kurds live outside PYD control. ISIS fighters have now surrounded Kobani, in Aleppo province, home to a large Kurdish population. The extremist group cut the municipal water supply there four months ago, with residents relying on local wells.

Analysts say that since last week, ISIS fighters have been moving weapons across the Iraqi border into Syria, likely to fortify their eastern push.

“There is a readiness for a possible attack that could be launched by ISIS targeting Kurdish cities,” Civiroglu says. “If such an attack comes, Hassakeh, Qamishli: these could be the possible targets. The impression I get is that they’re getting ready, they’re on high alert.

“Right now, Syrian Kurds right now are just trying to protect their border and prevent any attacks [on their territory.] But the spoils ISIS has won from the Iraqi army are a great source of concern for Syrian Kurds. They were transferred to the Syrian side, so ISIS will probably focus on expanding in Deir Ezzor and launching an offensive against Kurds in Hassakeh.”

Frustration has been simmering for months among Syrian Kurdish fighters and officials, who say that they have been fighting ISIS largely alone, the battle largely ignored until last week by their counterparts in Turkey and Iraq.

“Now that ISIS is showing its true colors in Iraq, it’s not a surprise for them in Syria,” Civiroglu says.

“The governor of Kirkuk [the Iraqi city now under peshmerga control], who is a well-known personality among Kurds, said Thursday saying that Kurds [in Iraq] were at fault for not supporting the YPG. He criticized his own party, including the KDP and even Turkey, saying YPG was left alone, was not supported while it was fighting ISIS.”

Among Iraqi and Turkish Kurds, there are now calls for the Turkish government to provide support to Syria’s Kurdish council. “The call on the street is for Kurds to all come together as one against ISIS,” McGee says.