Officials in London say Britain's domestic security agency, MI5, plans to increase its staff by up to 50 percent, to focus on the threat posed by terrorists.

The British security agency is expected to recruit at least 1,000 new workers, increasing its staff to levels not seen since the World War II.

New MI5 employees, including linguists and security experts, are to be assigned primarily to surveillance and counter-intelligence duties. British officials say they need greater intelligence resources to detect anyone linked to al-Qaida or other terrorist groups among the thousands of people who cross Britain's borders each day.

Government officials say British Home Secretary David Blunkett will announce the boost in domestic security in Parliament on Wednesday, during a debate on whether to extend a controversial law that allows detention of foreign terrorist suspects without trial. The British Labor government's political opposition, led by the Conservative Party, welcomed news of the intelligence agency's expansion, but said such a move was long overdue.

Prime Minister Tony Blair has faced sharp criticism at home in recent months for his decision to send British troops to Iraq and for his support of the war against terrorism. Mr. Blair is quoted as saying on Sunday that he intends to fight for a third term in office, despite opinion polls that show his popularity has declined sharply.

In a newspaper interview with the News of the World, a Sunday tabloid, Mr. Blair said the question of whether he is to remain prime minister is for the British people to decide in the next election. He called his job "immensely enjoyable and fulfilling."

Britain's next election must be held by mid-2006, but Mr. Blair could call for an early ballot before that date.