The Obama administration has increasingly warmed to a Russian proposal that allows U.S. forces to coordinate with the Kremlin in the ongoing war against ISIS in Syria. But the White House is facing major resistance to the idea from the U.S. military and those in the intelligence community who are working with local Syrian opposition forces—the very government officials who would carry out such a plan.

The pushback comes as the U.S. has reportedly sent a proposal to Russia to share information about specific target s to strike in Syria. Secretary of State John Kerry is scheduled to meet with Russian President Vladimir Putin Thursday in part to discuss the plan.

Some Pentagon officials already are saying it won’t work. They have suggested that should the U.S. and Russia agree to increased coordination, they will lobby to share as little with the Russians as possible.

There are discussions in the Pentagon about narrowing the extent of the coordination and the amount of intelligence shared, a U.S. defense official explained to The Daily Beast.

The Russians, two defense officials said, could not be trusted to honor any agreement, saying they believe Moscow would eventually exploit any agreement to bolster the regime—and weaken Syria’s beleaguered rebel fighters. As one U.S.official asked: “What do we gain?”

The internal debate about how much to expand U.S. coordination with the Russians has exposed perhaps the greatest schism within the administration this year over the way ahead in Syria.

Will it help end the war—and if so—for which side? Will it lead to a weaker ISIS and al Qaeda in Syria or an emboldened Russia and Syrian President Bashar al Assad?

The U.S. officials supporting increased coordination believe that ultimately Russia wants a political solution—an agreement between Assad and the rebels. Increased coordination could induce Russia to broker such a deal. On the ground, increased coordination could reduce civilian casualties and weaken terror groups like Jabhat al Nusra, al Qaeda’s affiliate in Syria, one administration official explained to The Daily Beast.

“The regime needs to... end the indiscriminate use of weapons, including the targeting of civilians and civilian authorities, and including medical ones. And we look to the Russians to make a greater use of the influence that we know that they have to make that happen,” State Department spokesman John Kirby explained to reporters last week.

But for others in the U.S. government, there are concrete reasons, presented in just the last few weeks, not to trust the Kremlin. Russia is believed to have attacked Pentagon-backed and trained forces in southern Syria last month, even after the U.S. reached out to the Russians to alert them about who they were striking. Russia denied striking the rebels, stationed near the Jordan border.

For others at the State Department, Russia is not a partner in Syria but the country whose police forces attacked a U.S. diplomat entering the embassy in Moscow over the weekend, leading to an expulsion and counter expulsion of diplomats.

The State Department said Russian police “attacked” the diplomats. Last month, Kerry raised the issue of how diplomats are being treated with the very Russian officials he is now discussing a military coordination plan with.

And in the nine months since Russia began its strike campaign on behalf of Assad, there have been a series of broken agreements.

In May, for example, there was an agreed ceasefire between Russia and the United States in the Syrian city of Aleppo. And yet, despite those calls to stop fighting, just over the weekend, with the help of Russian air strikes, the Syrian army claimed control of Castello Road, a key rebel route out of Aleppo.

The U.S. has been trying to get its Syrian rebel allies to separate themselves from Nusra, so far without success, because the Islamist group is among the most effective anti-Assad forces. The Russians have said that with the moderate rebels interspersed with Nusra, it’s hard to bomb al Qaeda without also bombing the moderate rebels. Moscow says it needs to know where the American-backed rebels are so its forces don’t hit them by accident.

Opponents to such coordination sense a Russian trap. Two U.S. defense officials explained to The Daily Beast that they believe the Russians will use such coordination to shift the discussion about Syria away from Assad’s removal and toward weakening his opponents, like Jabhat al Nusra. Moreover, they fear that once Russia, with U.S. help, pushes back the al Qaeda affiliate, they will renege on promises to spare the U.S.-backed moderate Syrian opposition, thereby “eliminating the two greatest threats to the Assad regime,” the U.S. official explained.

“Russia is framing this offer in terms of counterterrorism and is proposing joint operations against both Jabhat al Nusra and ISIS, but of course Russia’s current campaign does not actually make such distinctions. The issue on the table, therefore, is whether it’s possible for the U.S. to redirect Russia into an actual counterterrorism alliance in which Russia halts targeting of acceptable opposition groups,” Jennifer Cafarella, a Syria analyst at the Washington-based Institute for the Study of War, explained to The Daily Beast.

U.S. defense officials said that working with Moscow would give credibly to a far less precise Russian military air campaign, one that has, by everyone’s measure, killed far more civilians in Syria than the U.S.-backed coalition.

“Why give [the Russians] legitimacy?” one defense official asked.

And perhaps most importantly to those working with local forces, they fear that any agreement could cost the U.S. credibility with local forces who are working with them.

The U.S. and Russia already communicate to ensure there are no accidents in the air over Syria and that U.S.-backed opposition forces are not struck. There is no coordination of attacks, but rather an exchange of limited information to prevent unintended strikes.

The pressure on the Pentagon to embrace increased Russian coordination has begun to creep into the public discourse. Secretary of Defense Ash Carter, who once flatly closed the door to increased Russian coordination, opened that door ever so slightly late last month.

“If the Russians would do the right thing in Syria, and that’s an important condition, as in all cases with Russia, we’re willing to work with them,” Carter told reporters at a June 30 briefing.

The U.S. has been divided for years about how to deal with Nusra, which the U.S. declared al Qaeda in December 2012. The U.S. now sees the ongoing expansion al Qaeda affiliate as dangerous.

“In Syria, as [ISIS] is losing territory in the east, its terrorist rival—Jabhat al-Nusra—is gaining ground in the west,” Brett McGurk, the U.S. special presidential envoy for the Global Coalition to Counter IS, said June 28 in written testimony to the Senate Foreign Relations Committee.

Kerry arrives in Moscow Thursday, in part, “to test how serious the Russians are about using their influence in a constructive way in Syria,” a second U.S. official explained.