BEIRUT, Lebanon: Hezbollah headed by Hasan Nasrullah and an allied Christian political party led by General Michel Aoun are demanding a government reshuffle that would give them more positions -- and would in effect give Hezbollah veto power over any legislation.

They have threatened to boycott the government or try to bring it down through strikes and street demonstrations if they don't get more posts.

Analysts say Hezbollah's demand threatens a power-sharing arrangement that has averted civil war for 15 years, doling out positions of power to different groups without regard to their real share of voter support. Any challenge to that system would cause some sects to lose power and could unleash a new round of the bloodshed that gripped Lebanon from 1975 to 1990.

That system divides power among the country's main groups -- Shi'ites, Sunnis, Druze, and Christians.

US officials, the Lebanese government, and Israel say that by gaining veto power, Hezbollah would paralyze the government, extend Syrian influence over Lebanon, and ruin Lebanon's prospects to rebuild. And if Hezbollah -- which the US lists as a terrorist group -- were to expand its share of government power, the United States could find itself unable to work with the Lebanese authorities, since it boycotts all Hezbollah officials.

Political leaders in Hezbollah say the Shi'ites have proved that they command far more popular support than is reflected in their share of government posts under Lebanon's delicate power-sharing arrangement.