Sen. Bernie Sanders, I-Vt., is set to announce his decision to run for the Democratic nomination for the presidency as soon as Thursday, according to multiple reports.

Vermont Public Radio reported Tuesday that he was to announce his bid for the nomination on Thursday. The Associated Press also reported that the self-described socialist was planning on announcing a bid for the nomination, but did not specify a date.

A Sanders spokesman told Fox News that an announcement was coming Thursday, but wouldn’t say what it was as “we have to keep some suspense.”

A top Sanders aide also noted the senator had said previously that he would announce something by the end of the month – but wouldn’t comment further.

A Sanders campaign would offer the liberal wing of the Democratic Party a progressive alternative to frontrunner Hillary Clinton, after liberal favorite Sen. Elizabeth Warren, D-Mass., has repeatedly said she has no plans to run for the nomination.

Fox News’ Mike Emmanuel  and Whitney Ksiazek contributed to this report.