The union said late last week prior to the agreement that it was planning a Peabody protest because “that’s where this problem started”, according to president Cecil Roberts.

Patriot Coal was established as a spin-off company from Peabody in 2007 and the following year acquired Arch Coal spin-off Magnum Coal.

Union secretary treasurer Dan Kane was among the hundreds who attended the 10am rally at Kiener Plaza, across from the Peabody headquarters office.

In a presentation before the crowd, he said Peabody was still responsible for its former employees.

“We might come to some kind of agreement with Patriot, but that doesn’t end anything with Peabody,” Kane said.

“We said from the beginning that it’s not over until we say it’s over, and I’m telling you today, Peabody, it ain’t over.”

Roberts promised Monday night, on the eve of the event, that the rally would go ahead despite the Patriot agreement.

“We have reached a tentative settlement with Patriot Coal which will lessen the impact of severe cutbacks on active and retired miners, but as we’ve said all along, Patriot really is bankrupt and just does not have sufficient resources to pay for the contractual promises made to retired miners and their families by Peabody and Arch,” he said.

“Executives at Peabody Energy created Patriot, they failed to give it enough assets to meet its obligations, and we’re not going to sit idly by and let miners and their families pay the price.”

The union’s last demonstration was on July 30, when about 3000 mine workers and supporters protested outside Arch Coal’s headquarters in St Louis suburb Creve Coeur.

There were 10 arrests at the event for civil disobedience; no officials have confirmed any arrests from Tuesday’s protest.

Union members are planning to vote on the proposed deal with Patriot on Friday.