Bernie SandersBernie SandersSenate Democrats push for arms control language in defense policy bill Top adviser on Sanders: 'He's always been underestimated' 'The Simpsons' pokes fun at Trump's feud with 'the squad' MORE's presidential campaign has officially served the Democratic National Committee (DNC) with its lawsuit over access to party voter files, it said Thursday in a court filing.
U.S. District Judge Tanya Chutkan had given the campaign a Thursday deadline to serve the DNC with the suit or risk having it dropped from federal court.
In the new filing, the campaign said the two sides "continue to engage in cooperative discussions in their efforts to resolve the pending litigation" and will keep the court updated on those discussions. 
A source close to the Sanders campaign framed the latest development as a way to keep the door open for a lawsuit as the two parties wait for the results of an independent audit. 
But the source believes the issue ultimately will be "resolved amicably."
"We’re dealing with the DNC on an issue where we felt that they did not deal straight with us from the beginning, so the reason to keep this in place was to make sure Sen. Sanders is treated fairly in this process," the source told The Hill.
"This filing is very procedural. We went through with it because the report is not yet complete."
DNC spokesperson Mark Paustenbach echoed that optimism in a brief statement to The Hill.
“We continue to have productive discussions with the Sanders campaign and look forward to resolving this matter," he said. 
Sanders sued the DNC in December after the party briefly shut off his campaign's access to shared voter data. The committee was responding to the discovery that a Sanders aide had accessed separate data owned by rival Hillary ClintonHillary Diane Rodham ClintonThe Memo: Polls flash warning signs for Trump Polls suggest Sanders may be underestimated 10 declassified Russia collusion revelations that could rock Washington this fall MORE's campaign.
The since-fired Sanders aide said he was only trying to document a system error so it could be fixed, and the Sanders campaign has argued that even the brief interruption represented a serious blow.
The party agreed to restore access shortly after Sanders filed the lawsuit. But the campaign has not closed the door on the suit, which seeks $75,000 for breach of contract.
The dispute has highlighted tensions between the Sanders campaign and the DNC.
When access to the access to the data was initially shut off, the campaign denounced it as an overreaction and suggested the campaign was aiding Clinton's campaign. 
The Clinton campaign, in turn, attacked Sanders for what it called an "egregious" use of the DNC database.
“This was not an inadvertent glimpse into our data, not a mistake,” Clinton campaign manager Robby Mook said. “They made 25 intentional and targeted searches of our data.”  
Sanders is trailing Clinton in the race for the Democratic nomination, but hopes to make up ground this weekend in the contests being held in Washington state, Hawaii and Alaska.
- Updated at 7:02 p.m.