Britain is pushing a major diplomatic offensive this week against Zimbabwe President Robert Mugabe.

British Foreign Secretary Jack Straw is leading the push to isolate Mr. Mugabe with threats of economic sanctions and expulsion from the Commonwealth.

In an interview with The Guardian newspaper, Mr. Straw accused Mr. Mugabe of carrying out "a ruthless campaign to hang on to power."

Mr. Straw says Britain is increasing the pressure on Mr. Mugabe because of rising political violence against his opponents as the March presidential election approaches.

Britain favors targeted economic sanctions against Mr. Mugabe and his inner circle if he refuses to let international observers monitor election preparations. The sanctions could result in freezing Mr. Mugabe's European bank accounts, and ban his travel to Europe.

Britain also will tell the Commonwealth Ministers' Action Group on Wednesday that Zimbabwe should be expelled from the 54-nation organization, which includes Britain's former colonies.

Until last week, Mr. Straw had been reluctant to push for sanctions, fearing it would give Mr. Mugabe an excuse to bar international election observers.

Now, Mr. Straw says that further delay will only benefit Mr. Mugabe, while ordinary Zimbabweans suffer.

"Robert Mugabe has already imposed the most terrible economic sanctions on his own people by collapsing the Zimbabwean economy and, in the course of that, causing very serious damage to the economies of the rest of southern Africa," said the British official.

Mr. Straw says he expects Mr. Mugabe will accuse Britain of manipulating world opinion against his government.

But Mr. Straw says the pressure from Britain could lead to positive change, as it has already provoked some arguments inside of Mr. Mugabe's ruling ZANU-PF party.