LONDON (AP) _ Winnie Mandela said in a television interview that South African blacks regard the government's state of emergency as a ''total declaration of war'' that blacks plan to fight to the bitter end.

The wife of imprisoned black nationalist leader Nelson Mandela also called on the rest of the world ''to strangle our country'' economically to force an end to South Africa's apartheid policy of racial separation.

''We know of no other peaceful measure we could use to prevent the violence that is the order of the day in our country,'' she told Independent Television's ''World in Action'' program.

The interview, broadcast Monday night in Britan, was taped Sunday at Mrs. Mandela's home in Soweto, a huge black township outside Johannesburg. The government had banned journalists from entering black townships after it imposed a nationwide state of emergency June 12, but lifted the ban on Saturday.

The program's editor, Ray Fitzwalter, said, however, that free reporting still does not exist in the black townships because South African military helicopters have taken journalists in. He said the taped interview was smuggled out of South Africa.

A television commentator said Mrs. Mandela's decision to speak to journalists could bring up to 10 years in prison. The state of emergency makes ''subversive statements'' illegal, but the South African government left the identification of such statements vague.

''The oppressed people have regarded the present state of emergency as a challenge to the people and a total declaration of war,'' said Mrs. Mandela.

The state of emergency was imposed four days before the 10th anniversary of the Soweto uprising, when large anti-government demonstrations were expected.

''It is virtual imprisonment outside the prison walls and the state of emergency can do nothing less than promote the very situation the government is trying to prevent,'' said Mrs. Mandela.

She said security forces were occupying the townships, the government was interfering with telephone communication between the townships and the rest of the world, and the country was covered with roadblocks.

Mrs. Mandela said blacks stayed indoors June 16 because the government would have used the emergency rules against public gatherings ''as an excuse to kill indiscriminately innocent, unarmed men and women and children.''

Prime Minister P.W. Botha's government, she maintained, ''will fight to the last man'' rather than accept black majority rule.

''As much as the South African racist regime is prepared to fight to the last man, so are we determined to fight to the bitter end,'' she added.

Mrs. Mandela said police had rounded up the entire leadership and virtually every activist in the United Democratic Front, the main anti-apartheid group, ''and almost every activist from every other organization is inside.''

She criticized British Prime Minister Margaret Thatcher and President Reagan for opposing additional economic sanctions. Both leaders have insisted that sanctions are counter-productive and will hurt South Africa's 24 million blacks.

''It is not for the British and the Reagan administration to prescribe to us what degree of suffering we must still undergo,'' Mrs. Mandela said. ''We have suffered enough.''

White House chief of staff Donald T. Regan, said today on NBC's ''Today'' program that economic sanctions against South Africa could backfire.

''We've got to be very careful there because that could hurt the blacks more than the whites,'' Regan said. ''If we start an economic sanction and buy nothing from South Africa, that throws an awful lot of people out of work.''

Mrs. Mandela declared that ''the African National Congress is the future government of South Africa, and that is God's foregone conclusion.''

The outlawed African National Congress, of which Nelson Mandela and Oliver Tambo are co-founders, is the main guerrilla group fighting to end the apartheid, a system of racial segregation in which 5 million whites dominate 24 voteless blacks.

A delegation from the 49-nation Commonwealth association of Britain and its former colonies failed this month to arrange negotiations between the ANC and the South African government.

In a speech to the Royal Commonwealth Society on Monday, Tambo appealed to the West to adopt economic sanctions, and urged Britain to take the lead.