This liberalization, however, fostered nationalist movements and ethnic disputes within the Soviet Union. It also led indirectly to the revolutions of 1989, in which Soviet-imposed communist regimes of the Warsaw Pact were peacefully toppled (Romania excepted), which in turn increased pressure on Gorbachev to introduce greater democracy and autonomy for the Soviet Union's constituent republics. Under Gorbachev's leadership, the Communist Party of the Soviet Union in 1989 introduced limited competitive elections to a new central legislature, the Congress of People's Deputies (although the ban on other political parties was not lifted until 1990).