(CNN) Federal prosecutors in Tucson, Arizona, said in court Tuesday that they were dropping a charge of conspiracy to transport "illegal aliens" against humanitarian aid worker Scott Warren, but will seek to retry him on two charges of "harboring illegal aliens."

Warren's first trial on those three charges ended in a mistrial June 11, after jurors told US District Court Judge Raner Collins they couldn't reach a verdict . Eight of the 12 jurors had favored acquitting Warren of all charges. That trial drew widespread attention over concern that it represented an effort by the Trump administration to criminalize humanitarian aid work.

In court Tuesday, prosecutors unexpectedly offered a plea bargain to Warren, saying they would drop the two felony harboring charges if he would plead guilty to a misdemeanor charge of aiding and abetting illegal entry without inspection, according to court records. Prosecutors said they would not seek to have Warren serve any time behind bars, Greg Kuykendall, Warren's defense attorney, said. A spokesperson for the US attorney's office confirmed the developments but was unable to say whether the offer included no jail time for Warren.

Kuykendall said it will be up to his client whether to agree to the offer or go to trial, now scheduled to start November 12, on the harboring charges.

"While I do not know what the government has hoped to accomplish here," Warren said in a written statement," I do know what the effect of all this has been. A raising of public consciousness. A greater awareness of the humanitarian crisis in the borderland. More volunteers who want to stand in solidarity with migrants. Local residents stiffened in their resistance to border walls and the militarization of our communities. And a flood of water into the desert at a time when it is most needed."

Read More