Attorneys for embattled Sen. Edward W. Brooke (R-Mass.) and his wife Remigia, continued negotiations on a new divorce settlement yesterday under pressure of a deadline this morning for her decision on whether to undertake a new divorce trial.

A new trial could be politically devastating to Brooke, who faces an increasingly tough primary election battle in his bid for a third term because of his admitted "misstatements" concerning his finances in connection with the divorce.

Middlesex County Probate Judge Lawrence T. Perera - who on June 15 gave Mrs. Brooke the option of a new trial, with 10 days to decide - granted a request yesterday by attorneys for both sides to extend the deadline until this morning.

Meanwhile Brooke's attorney, Robert F. McGrath, filed an appeal of the judge's decision to offer Mrs. Brooke a new trial. The senator's press secretary, Robert Waite, called this "a hedge against no settlement" by this morning.

However, Waite said, there appeared to be an even chance that a settlement would be reached before the deadline.

A better settlement could help limit the senator's political damage by sparing him an acrimonious and highly visible divorce trial in the heat of his reelection campaign.

The judge, who reopened the divorce case on May 30 in light of Brooke's admitted misstatements under oath about his finances, said the senator's false testimony could have misled his wife about his assets before the original settlement was reached.

Under that settlement - granted on Dec. 15, 1977, and originally set to take effect June 15 - the senator would have had to pay his wife $18,000 a year in alimony, pay for her medical insurance and give her the couples homes in Newton, Mass., and St. Maarten in the West Indies.

Negotiations yesterday, according to Waite, focused on Mrs. Brooke's request that the senator pay all legal, medical and dental bills, the mortgage on the Newton home and about $80,000 in transfer taxes on the St. Maarten home, estimated to be worth between $300,000 and $400,000.

On Sunday, he said, the talks "looked grim - the two sides were pretty far apart." However, by last night there was a "50-50 chance of a new agreement. We've made some major concessions. It's a generous offer," Waite said, refusing to comment further on the specific proposal.

The Middlesex district attorney announced an investigation two weeks ago into possible perjury charges against the senator.

Brooke also faces investigation by the Senate Ethics Committee for omitting from his Senate financial statement a $49,000 personal loan that he listed on a court deposition during his nearly two-year-old divorce case. Brooke admitted that he made a "mistake and a misstatement" about the loan.

Meanwhile, the state welfare department is looking into possible Medicaid fraud involving his late mother-in-law's transfer of assets to him. And the state tax department is auditing the income tax returns of the senator, who used to be attorney general of Massachusetts.