What you need to know:
- Some 50 countries have recognised Guaido as leader while others continue to back President Nicolas Maduro.
- Maduro has vowed to prevent what he calls a "fake" aid "spectacle," seeing it as a precursor for an US military intervention.
- To block the entry of opposition-collected aid, Venezuelan authorities have closed the maritime border and suspended links with Curacao and the nearby Netherlands Antilles islands of Aruba and Bonaire.
- Venezuelan soldiers killed two people when they tried to prevent the troops from blocking an entry route for aid on the Brazilian border, a rights group says.
Opposition chief Juan Guaido stunned the world on January 23 when he declared himself acting president of Venezuela, plunging the crisis-hit country into new turmoil.
Some 50 countries have since recognised him as leader while others continue to back President Nicolas Maduro.
Here is a recap of key developments over the past turbulent month.
On January 23, at a rally in Caracas of tens of thousands of people demanding that Mr Maduro quit, Mr Guaido -- head of the opposition-controlled National Assembly -- declares himself to be acting president.
Condemning Mr Maduro's "usurpation" of power, he pledges to form a transitional government and hold free elections.
US President Donald Trump immediately recognises Guaido, as do Canada and major Latin American powers.
Venezuela's opposition, Washington and other countries had already dismissed as fraudulent the May 2018 election that gave Mr Maduro a second term, which started January 10.
Mr Maduro gets the support of allies such as China, Cuba, Mexico, Russia and Turkey.
On January 24 Venezuela's military high command also throws its weight behind Mr Maduro.
On January 26 six European countries say they will recognise Mr Guaido as president unless Mr Maduro calls elections within eight days.
On January 28 Washington imposes sanctions on Venezuela's state oil company PDVSA.
The following day it hands control of Venezuela's bank accounts in the United States to Guaido.
The Venezuelan judiciary bars Mr Guaido from leaving the country and freezes his accounts.
The United Nations says protests the week before left more than 40 people dead.
On January 30 thousands of opposition protesters, led by Mr Guaido, call on Venezuela's military to abandon Mr Maduro and allow much-needed humanitarian aid into the country.
Mr Guaido presents a "rescue plan" to address Venezuela's "humanitarian emergency".
On February 2 tens of thousands of people demonstrate in Caracas, some demanding Mr Maduro's resignation and others celebrating the 20th anniversary of the start of the socialist presidency of his mentor and predecessor, Hugo Chavez.
On February 4 some 20 European countries recognise Mr Guaido, after Mr Maduro rejected their ultimatum to announce new presidential elections.
From February 7 the Venezuelan army blocks the Tienditas bridge on the border of Colombia where several vehicles loaded with food and medicines are waiting to enter the country.
Mr Maduro vows to prevent what he calls a "fake" aid "spectacle," seeing it as a precursor for an US military intervention.
On February 12 Mr Guaido announces that US aid will enter Venezuela on February 23, which would be one month since he declared himself to be president.
Washington says 25 countries have pledged $100 million in aid to Venezuela.
On February 16, Mr Guaido says that he has enlisted the support of thousands of people to help bring in aid from Colombia, Brazil and the Dutch island of Curacao.
On February 19 Mr Guaido calls on military chiefs to choose "between serving Mr Maduro or serving the homeland."
To block the entry of opposition-collected aid, Venezuelan authorities close the maritime border and suspend links with Curacao and the nearby Netherlands Antilles islands of Aruba and Bonaire.
On February 21 Mr Maduro also shuts the border with Brazil, another potential aid entry point, and threatens to close that with Colombia.
Mr Guaido sets out in a convoy of vehicles to personally pick up US aid being stockpiled on the other side of the Colombian border, defying Mr Maduro's military to stop him.
On February 22 Russia accuses the United States of using aid deliveries to Venezuela as a ploy to carry out military action against Mr Maduro's government.
Venezuelan soldiers kill two people when they tried to prevent the troops from blocking an entry route for aid on the Brazilian border, a rights group says.
An aid benefit organised by British billionaire Richard Branson is attended by thousands on the Colombian side of the Tienditas bridge.
Mr Maduro had announced a rival concert hundreds of yards (meters) away on the Venezuelan side of the border.