MONTPELIER, Vt. – Union leaders are urging the Legislature to investigate the sale of Verizon telephone lines to FairPoint Communications before the deal is approved by state regulators.

The $2.72 billion deal to buy lines in Vermont, New Hampshire and Maine will greatly expand the Charlotte, N.C.-based company’s number of telephone lines and workers.

“We don’t think they have the resources to pay for the debt they are going to acquire,” Mike O’Day, district vice president for the Communication Workers of America, said at a Wednesday rally at the Statehouse.

“Are they going to go bankrupt or sell us again?” asked Mike Spillane, business manager of the International Brotherhood of Electrical Workers Local 2326. “We are down here advocating for ourselves, but we are also advocating for the state.”

The unions represent 2,800 Verizon workers in the three states.

FairPoint executives said they believe the deal is viable.

“Wall Street looked at the deal and thought it was a very good and sound investment,” said Walt Leach, executive vice president for corporate development.

The company will partly finance the deal by offering $1 billion in common stock. The addition of employees, high-speed Internet infrastructure, and maintaining wages and prices were considered when the deal was struck, company officials said.

“We are willing to state today we are not going to be reducing pay or benefits as part of the negotiations,” said Peter Nixon, chief operating officer of the company.