A group of residents that has fought for two years to prevent the Vallco Shopping Mall from being redeveloped into anything other than a retail hub announced Monday it has launched a referendum drive to stop the latest plans to turn the ailing shopping center into a massive mixed-use project.

At almost the same time and at the same place, proponents of a community-forged proposal to build housing, retail and offices at Vallco held a press conference to galvanize public support for their vision and cautioned that further delays could hurt the city’s future.

Meanwhile, Vallco’s owner and developer, Sand Hill Property Co., said it could start a phased demolition of the shopping mall in the next few months, even though it hasn’t decided whether to accept the community plan or proceed with its original plan under the auspices of Senate Bill 35.

Monday’s statements came in the wake of two important actions last week. On Friday night, the city of Cupertino accepted Sand Hill’s proposed mixed-use plan to keep it on track.

And two days earlier, the City Council voted 3-2 to approve the community’s alternate proposal for Vallco, which calls for different ratios of housing, retail and office space but also seeks a package of benefits including a major performing arts center, a new city hall and emergency response center, and multimillion-dollar contributions to the city’s schools.

Reed Moulds, Sand Hill’s managing director, warned last week that any delay of the project would be costly for the company and possibly force it to cut back on potential community benefits.

Members of Better Cupertino, a community group that has strongly opposed every Vallco proposal that includes housing or office, characterized Sand Hill’s warning as “blackmail.”

Ignatius Ding, a Better Cupertino leader, said the group doesn’t want a referendum but the city’s actions leave it with no other recourse. He also criticized the community’s alternate plan process, which was developed under the guidance of architecture and urban design firm Opticos, as unfair and inefficient.

“When we said we want retail, they’d write ‘mixed-use,’ ” he complained.

So far, a petition asking people to support a referendum has collected 350 signatures, he announced at a press conference outside Hong Fu restaurant ahead of a separate press conference held inside in support of the community-drawn plan. Better Cupertino has also raised enough money to pursue two separate, but related lawsuits, he said.

The dueling press conferences drew a little over a dozen supporters of Better Cupertino, including Councilman Steven Scharf, who along with Mayor Darcy Paul voted against the project last week.

“We would love not to have a referendum,” Scharf told this news organization Monday. “The majority of residents prefer a project that is less dense, is jobs-housing balanced and provides continuous funding for schools. We still have an opportunity to do that.”

He added, “I don’t know how many times we’re going to vote on the same thing, but if we have to…”

Inside Hong Fu, about 70 people gathered to listen to Vice Mayor Rod Sinks and council members Savita Vaidhyanathan and Barry Chang explain why they voted for the alternate plan. The gathering was organized by Hung Wei, a Fremont Union High School District trustee who is running for City Council. Her opponent and former Cupertino Mayor Orrin Mahoney also attended.

Sinks urged the gathering to consider what kind of community they want to live in and dismissed Better Cupertino’s gripes, saying “there was no constructive engagement from their side” throughout the planning process. He also accused the group of spreading “alternative facts.”

“Frankly they’ve been obstructionists all this time,” he said.

Assemblyman Evan Low, who said he happened to be dining at the restaurant, was also pulled in to give a short speech. He told the crowd that Sand Hill’s plan for Vallco would put Cupertino “on the map internationally” and ensure that future generations could continue to afford living in the cities they were raised in.

Mike Malik, a 43-year resident, said the problem is that Better Cupertino is better organized than the collective that supports the development projects.

“They need to counter the tactics and strategies of Better Cupertino,” he said. “It will take raising funds; it will take motivating volunteers to knock on doors — which Better Cupertino does so well — and it will take dispelling the convenient truths that these guys distort to get their own way.”

The community plan comes up for a second reading on Oct. 2.