CONCORD, N.H., DEC. 9 -- A major creditor pushed the Public Service Co. of New Hampshire one step closer to bankruptcy court today when it called in a $425 million bond issue that is in default.

The New York Stock Exchange suspended trading in PSNH stock and bonds for several hours after Midlantic National Bank of Edison, N.J., the sole trustee for the 17 1/2 percent debentures due in 2004, demanded payment of the principal and accruing interest.

PSNH, the principal owner of the stalled Seabrook nuclear power plant, skipped a $37 million interest payment on the notes on Oct. 15, becoming the first major investor-owned utility to default since the Depression.

Under terms of the loan agreement, creditors may demand payment of principal and interest 30 days after any interest payment is skipped.

PSNH spokesman Nicholas Ashooh said the utility would not pay the $425 million in principal.

"We're not in a position to pay that," he said. "That's why we didn't pay the interest."

Ashooh said Midlantic's move would not prompt PSNH to seek bankruptcy protection voluntarily, and he reiterated the utility's hope that a judge would put any involuntary bankruptcy petitions on hold while out-of-court reorganization efforts are in progress.

Midlantic spokesman Charles Ward would not comment on whether the bank would launch involuntary bankruptcy proceedings against PSNH, New Hampshire's largest power company.

A Wall Street analyst, Daniel Scotto of L.F. Rothschild, said, "This action per se does not lead to {an involuntary bankruptcy filing}, but it is one step closer to that happening."

Ward said Midlantic wrote to PSNH Nov. 24 demanding the interest payment by Dec. 4, then demanded payment of interest and principal after the close of business Tuesday.

PSNH's woes stem from its $2.1 billion investment in the $5.1 billion Seabrook nuclear reactor, which is completed but sits idle, unable to overcome evacuation-planning obstacles to an operating license.

New Hampshire law bars utilities from charging ratepayers for power plants before they operate commercially.

PSNH, which seeks an emergency $71 million rate increase as part of its survival effort, has asked the state supreme court to overturn that law, and oral arguments are scheduled for next week.

PSNH also is trying to restructure its debt, and offered one proposal to do so in September.

However, a dissident bondholders' group squelched that deal and the utility is revising the plan.

The New York Stock Exchange suspended trading in PSNH stock and bonds at the opening this morning after Midlantic made its demands.

Trading resumed at about 1 p.m., and PSNH common stock closed at 3 1/4, down 1/2, while the 17 1/2 percent debentures closed down 1 3/4 at 29 1/4.