Supporters of Democratic presidential candidate Bernie Sanders at the Nevada State Democratic Party’s convention in Las Vegas. Tension erupted between organizers and supporters. (Chase Stevens/Las Vegas Review-Journal via AP)

In an attempt to head off an ugly conflict at its convention this summer, the Democratic National Committee plans to offer a concession to Sen. Bernie Sanders — seats on a key convention platform committee — but it may not be enough to stop Sanders from picking a fight over the party’s policy positions.

Allies of both Clinton and Sanders have urged Democratic leaders to meet some of Sanders’s more mundane demands for greater inclusion at the Philadelphia convention. Their decision to do so is expected to be finalized by the end of the week, according to two people familiar with the discussions. But growing mistrust between Sanders supporters and party leaders have threatened to undermine that effort.

Even with the committee assignments, Sanders plans an aggressive effort to extract platform concessions on key policies that could prompt divisive battles at a moment when front-runner Hillary Clinton will be trying to unify the party. Among other issues, he plans to push for a $15 national minimum wage and argue that the party needs a more balanced position regarding Israel and Palestinians, according to a Sanders campaign aide who requested anonymity to speak candidly.

Much like their view that the economy has been “rigged” to benefit the wealthy more than the middle and working classes, Sanders supporters have become increasingly convinced that national Democrats have stacked the political deck with rules that have made it difficult for Sanders to win enough delegates to threaten Clinton’s nomination.

Party leaders, meanwhile, have grown more frustrated with Sanders, who they say has unfairly fueled that perception.

“I don’t think they’ve handled it very well and I think they’ve lost the moral high ground on this,” said Ken Martin, chairman of Minnesota’s Democratic-Farmer Labor Party. “It’s very clear now that the longer they stay in this race the more damage they’re doing.”

The Nevada Democratic convention on May 14 didn't go smoothly. The Fix's Philip Bump breaks down what happened. (Peter Stevenson/The Washington Post)

The mistrust hit a boiling point in Nevada over the weekend, when a ruckus caused by Sanders supporters prompted security officials to cut short the state party convention. The incident worried party leaders impatient with the prolonged Democratic primary and looking to avoid drama in Philadelphia. Their impatience spread to Sanders when he issued a defiant statement accusing Nevada Democrats of preventing a “fair and transparent process.”

Separately, the composition of three convention committees — platform, rules and credentials — has become key. Earlier this month, in a letter to DNC Chairwoman Debbie Wasserman Schultz, Sanders threatened to bring the fight to the floor of the convention if she did not appoint more of his loyalists to the each of the three committees.

Martin and other Democratic chairmen urged national leaders to give Sanders the concessions he seeks — especially when it comes to the platform, which in the long run does not have a material impact on Democrats’ electoral chances in November.

“There are other chairs who probably feel that way and feel like this is my party and f--- Bernie Sanders,” said Martin, a Clinton supporter. “I’m not one of those.

“I feel very passionately that we have to open up that party and make sure that those voices are heard,” he said.

One of Sanders’s demands was the composition of the 15-person drafting committee, whose members are appointed at Wasserman Schultz’s discretion and write the party’s platform.

One Democratic Party official requesting anonymity said Wasserman Schultz asked for recommendations from both campaigns in an effort to be inclusive.

But Sanders had sought to split the committee evenly between his and Clinton’s allies — plus one “neutral” appointment from Wasserman Schultz.

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Weeks of negotiations followed, and the DNC eventually agreed to add more Sanders representatives. According to two people familiar with the conversations, the DNC and the campaigns will reach a final agreement — probably less than Sanders wanted but more than the DNC originally offered — by the end of the week.

A spokesman for the DNC declined to comment on the negotiations.

Sanders’s aides have also publicly and privately complained about the appointment of two Clinton loyalists — former congressman Barney Frank of Massachusetts to head the Rules Committee and Connecticut Gov. Dan Malloy to lead the Platform Committee — as chairmen of two of the convention’s standing bodies.

Tad Devine, a senior adviser to the Sanders campaign, said this week that they may yet seek to have Frank and Malloy removed from their posts.

In an interview with CNN Thursday, Clinton noted pointedly that she believes Sanders no longer has a shot at the nomination. She also said that Sanders will need to encourage his supporters to unify behind her, just as she did in 2008 when running against Barack Obama.

“I have every confidence that we’re going to be unified,” Clinton said. “I think what brings us together is Donald Trump.”

That hasn’t happened yet. A Sanders spokesman disputed Clinton’s assertion that the nomination is hers. And Sanders has ramped up the rhetoric in recent days, saying after Clinton won Kentucky that he still intends to win the nomination despite an overwhelming disadvantage in delegates.

In front of a boisterous crowd in Carson, Calif., Democratic presidential candidate Bernie Sanders called on the Democratic party May 17 to "open the doors; let the people in." Sanders vowed to continue fighting rival Hillary Clinton for the party's presidential nomination. (Sarah Parnass/The Washington Post)

Even if he doesn’t, he still intends to pick a platform fight at the convention, according to a campaign aide who requested anonymity to discuss strategy.

Clinton aides have said that on a slew of issues, Sanders is not far from the party. But the issue of U.S. policy toward Israel — which a Sanders adviser said “absolutely, legitimately will be a point of conversation” — has made some of Clinton’s backers nervous.

Sanders is seeking a more “even-handed” U.S. approach to Israeli occupation of land Palestinians claim for a future state. The current platform does not address the nearly five-decade occupation directly, but it endorses “a just and lasting Israeli-Palestinian accord, producing two states for two peoples.”

Speaking last month during a contentious debate with Clinton, Sanders — who declared himself “100 percent pro-Israel” — said that Israel’s 2014 military assault on the Gaza Strip was “disproportionate” to the threat posed by Hamas rockets launched from the Palestinian territory into Israel.

Behind his words is a long debate among U.S. and international policymakers — one that divides the Democratic base and could pose a challenge for Clinton when she must bring her party together: how to weigh Palestinian interests when dealing with Israel, and whether resolute U.S. backing for Israel diminishes leverage to promote peace and fair treatment of Palestinians.

“On one hand there is not an enormous amount of difference between them. They are both pro-Israel, they are both pro-peace,” said one longtime Clinton supporter. “But in the context of the campaign terms like ‘even-handed’ can come to mean that the United States is signaling a shift” — and Clinton would oppose that.

anne.gearan@washpost.com