Caracas - Venezuela's new pro-government constitutional authority formally declared on Friday it was seizing power from the opposition-led legislature, tightening President Nicolas Maduro's grip on the country in defiance of international outrage.It was the latest manoeuvre in a deadly political crisis that has seen Maduro branded a dictator by opponents whom he in turn accuses of plotting with the United States to overthrow him.The Constituent Assembly (NCA) unanimously adopted a decree authorising it to "take over functions to legislate on matters directly concerned with ensuring peace, security, sovereignty, the socio-economic and financial systems, state assets and upholding Venezuelans' rights."The opposition-led National Assembly rejected the move, branding it a "coup d'etat.""The National Assembly, the international community and the people will not respect the decision to annul" the legislature's powers, the body said on its official Twitter account."The NCA is null and its acts are illegal and unconstitutional."Supreme public power The centre-right opposition says the new constituent assembly is a ploy by Maduro to tighten his grip on power.It was ostensibly set up to rewrite the constitution but has been handed sweeping powers to override all other branches of government."All the organs of public power are subordinate to the National Constituent Assembly," said the decree, read out at Friday's session.The body's 545 members, all Maduro allies, were elected on July 30 in polls marred by violence and allegations of fraud.The assembly - led by Maduro's fiercely loyal former foreign minister, Delcy Rodriguez - also includes his wife and son."We will not permit any more diverting of power" by the opposition, Rodriguez said Friday before the decree was read out."The constituent assembly is here to impose order."International concern International powers have accused Maduro of acting undemocratically.Several Latin American countries have said they will not recognize the Constituent Assembly or its decisions.The United States has imposed direct sanctions on Maduro.The socialist leader was elected in 2013 but is facing calls to quit from opponents angry at an economic crisis that is causing hunger and deadly violence.Nearly 130 people have been killed this year in a wave of anti-government protests.The legislature - controlled by the opposition since late 2015 - was the last state institution still not held by Maduro's allies.The constituent assembly was set up for a period of two years, meaning it would retain its powers beyond the end of Maduro's elected term in office, which ends in 2019."Beyond just rewriting the constitution, it is turning itself into the de facto legislative body," said Diego Moya-Ocampos, a Venezuelan analyst with consultancy IHS Markit."That was one of the areas the government was looking to finally control."One of Maduro's fiercest international critics, the leader of the Organization of American States Luis Almagro, called for a special meeting of the body in response to the latest moves.He denounced what he called the "fraudulent dissolution" of the legislature.US force threat US President Donald Trump warned a week ago that that he was considering various options to resolve the Venezuela crisis, "including a possible military option if necessary."His Vice President Mike Pence softened that stance this week during a tour of Latin American countries.He said he was sure democracy could be restored in Venezuela through economic and diplomatic pressure.Various regional powers have joined in condemnation of Maduro but rejected any use of force to resolve the crisis.The opposition leaders in the National Assembly called a session for Saturday morning.