BEIJING, April 8 (Reuters) - Several Chinese state

holding companies on Tuesday vowed to increase share investment

as Beijing steps up efforts to stabilize a plunging stock market

on U.S. tariff woes.

The announcements by China Chengtong Holdings Group

and China Reform Holdings Corp came after Chinese

state fund Central Huijin said on the previous day it would

increase share holdings to foster stability in markets.

China's stock benchmark dived 7% on Monday amid

investor worries about the risk of a damaging trade war and a

global recession.

Washington last week imposed extra tariffs of 34% on China,

which then fired back with its own 34% levies on U.S. imports.

Chengtong said its investment units will increase holdings

in stocks and exchange traded funds (ETFs) to safeguard market

stability.

"We are firmly optimistic toward the growth prospects of

China's capital markets," the state investment firm said in a

statement, vowing to support high-quality growth of Chinese

listed companies.

China Reform Holdings Corp, also known as Guoxin, said in a

separate statement that an investment unit will increase

holdings in tech companies, state firms and ETFs, tapping a

relending scheme for share buybacks. Initial investment will be

80 billion yuan ($10.95 billion).

Another state holding company, China Electronics Technology

Group, said it will boost share buybacks in listed units to

bolster investor confidence.

($1 = 7.3081 yuan)