Four men have admitted being involved in a conspiracy to cause explosions on dates in 2001 and 2004 during a hearing at Woolwich Crown Court.
Dhiren Barot was jailed for life last year
Junade Feroze, 31, Zia Ul Haq, 28, Abdul Aziz Jalil, 34, and Omar Rehman, 23, all pleaded guilty to an offence under the explosives substances act.
They are alleged to have taken part in a plot involving Dhiren Barot.
Barot was sentenced to life in prison last year for planning explosions in the United States and Britain.
A fifth man, Mohammed Naveed Bhatti, admitted being involved in a terrorist plot to cause explosions at a previous hearing.
The men will be sentenced at a later date.