UPDATE 1-Venezuela constituent assembly assumes power to legislate

(Adds quote on decision, context)

CARACAS, Aug 18 (Reuters) - Venezuela's constituent assembly on Friday gave itself the power to pass laws, superseding the opposition-led congress and fueling criticism that the new all-powerful legislative superbody is undermining democracy in the crisis-stricken country.

"The constituent assembly ... decrees that it will assume the power to legislate on issues directly related to preservation of peace, the socio-economic financial system ... and the preeminence of Venezuelans' human rights," read a decree, which was approved unanimously.

In practice, the move does little to change the existing situation. The Socialist-dominated Supreme Court has stripped congress of powers and shot down nearly every law it has approved since the opposition took control of it in 2016.

But the decision suggests the constituent assembly, elected in July in a vote boycotted by the opposition, is more interested in limiting the opposition's political influence than rewriting the constitution, which is its official task.

The assembly had invited leaders of the existing congress to join the session. Congressional leaders did not attend the session, insisting it was fraudulently created and usurping their powers.

"(Congress) only obeys the constitution and the people. We do not recognize the constituent assembly, much less subordinate ourselves to it," wrote opposition politician and congress Vice President Freddy Guevara via Twitter. (Reporting by Brian Ellsworth; Editing by Jeffrey Benkoe)