President Carter moved yesterday to help New York end the continuing anguish of the Love Canal toxic dump by offering a $15 million loan to finance purchase of the residents' contaminated homes.

If New York accepts, the people of Love Canal could move out of the area permanently. Carter declared a state of emergency and authorized temporary housing for the residents in May, but the 700 families have insisted they can never live atop the dump again.

New York had asked for an interest-free $20 million loan. "It's not exactly what we were talking about, but we will certainly look at it," said Charles Holcomb, Gov. Hugh L. Carey's communications director. "We are definitely pleased that the government is responding to what we've been telling them for a long time is needed."

Residents of the Love Canal area of Niagara Falls have suffered abnormal rates of miscarriage, birth defects and chronic illness over the years since their homes were built in the 1960s. After a recent study found that some residents had suffered chromosome damage, their panic led to the declaration of emergency. They have been trying to get government help to move since the old chemical dump was discovered in 1978.

The administration's offer came in an evening telegram from John Macey, head of the Federal Emergency Management Administration (FEMA), to New York's Disaster Preparedness Commission head, William C. Hennessy. Hennessy had proposed on June 18 that Washington provide funds to enable the Love Canal people to move out.

Instead, FEMA offers, a $15 million loan to be repaid over 30 years at an interest rate of 8.25 percent. Macey suggested that Niagara Falls apply for a "reallocation" of $7 million in unspent funds it has already received from the Department of Housing and Urban Development under the community development block grant program.

HUD would look favorably on such a reallocation request, Macey indicated.

Addition of a $5 million grant that has been offered to Niagara Falls by New York State would make the available total $27 million. "I think that would be enough" to buy the 525 homes involved Holcomb said.

The state already has spent $35 million to buy an additional 200 houses at Love Canal and to construct drainage ditches and cap the dump site. h

Sources close to the issue said Carter was unable to act before this for lack of loan authority. But Sen. Jacob JAVITS (R-N.Y.) added an amendment to FEMA's 1980 supplemental appropriation allowing emergency funding on the basis of 75 percent federal and 25 percent state participation. The $15 million loan would come out of that FEMA money.

Holcomb said the offer would have to be reviewed at both the state level and by Niagara Falls Mayor Michael O'Laughlin, who also is chairman of the Love Canal agency through which other funding has been channeled.

What to do about Love Canal has tied government in knots at both state and federal levels for two years. Reluctant to set an expensive precedent by moving out an untested group of people who complained of unverified illness, various agencies have infuriated the residents with what seemed to be interminable tests, studies, reports and debate.

Once relocated, many residents continued to complain that they had been shabbily treated and had been told conflicting tales by agencies worried about jurisdiction and cost.