As Harvard’s battle to build a new government center reaches feverish pitch, the fate of its most important building project hangs in the balance.

Tonight the Cambridge City Council will meet to consider Harvard’s proposal to tunnel under a city street and connect the two main buildings of its planned Center for Government and International Studies (CGIS).

As recently as this winter Harvard officials had maintained that construction work on the new center would be underway by now. But they now concede they don’t have the votes they need on the council to clear the final hurdle—permission to dig the tunnel.

The five-year-long struggle will continue long after tonight’s meeting ends.

An all-out effort in recent months by the University to win permission for the tunnel has intensified—all geared toward tonight’s meeting of the city council, the first time Harvard will publicly present its case to the body that ultimately will decide the tunnel’s fate.

Tonight some of the University’s top administrators will head to City Hall, where Cambridge residents have promised they will turn out in full force to make their case against the tunnel.

In recent weeks, the University’s public affairs officials have mailed pamphlets about the tunnel to city councillors and scheduled one-on-one meetings—and even the architect who designed CGIS has personally met with councillors to sell his plan.

“We’ve been meeting with councilpeople, we’ve been talking to community groups, we’ve done mailings of materials to councilpeople and neighbors,” said Vice President for Community, Government and Public Affairs Alan J. Stone.

The personal push has even come from University President Lawrence H. Summers and, while Stone would not discuss Summers’ involvement, he did say that “discussions like these go better if they are made privately and not discussed in the press.”

Despite its lobbying efforts, the outlook remains bleak that the University will obtain digging rights, as most councillors have publicly said they oppose the tunnel.

But several councillors said yesterday they are not ready to give the tunnel an up-or-down vote yet. They say they want more time to consider the pros and cons of Harvard’s plans and possible compromises—which neighborhood activists say they will offer at tonight’s meeting.

“I’m not ready to vote for it, I know that for sure,” said councillor Henrietta Davis.

Davis said she hopes to convince the council to hire consultants to evaluate how tunnel construction would affect the neighborhood and how utilities would have to be rerouted.

And eventually, she said, the consultants’ work could be the basis for a plan that would satisfy both sides.

“It would be nice to have a neighborly settlement take place,” Davis said.