KARACHI, 10 May — US Ambassador to Pakistan Wendy Chamberlain will be leaving for Washington next week, cutting short her assignment to a country which she once said she loved to be in. She now feels that being a mother she cannot live without her children for very long.

She will be replaced by another woman, Nancy Williams, officials here said. They said that the State Department does not allow American diplomats to keep their families in Pakistan for security reasons.

The wife and children of US consul general in Karachi John Bauman have also left for home.

Bauman is trying to bring back his wife because he says he intends to live here for three years. US authorities have advised their nationals to be careful while traveling to Pakistan on business or private trips because of recent attacks on foreigners.