Venezuela’s opposition movement can achieve a peaceful transition from President Nicolás Maduro and eventually hold free elections, its leader, Juan Guaidó, has said.

“We are sure we can achieve a peaceful transition – a transition and eventually free elections,” Guaidó said told CNN on Tuesday in a Spanish-language interview that was translated into English.

“We must use great pressure for a dictator to leave, install a transitional government and have free elections,” he said.

Guaidó, who has led the movement against Maduro, having declared himself interim president with support from the US and other western nations, spoke after Washington on Monday imposed sweeping sanctions on the state-owned oil firm PDVSA as it pressured Maduro’s socialist government.

The US national security adviser, John Bolton, said $7bn (£5.3bn) of PDVSA assets would be immediately blocked as a result of the sanctions while the company would also lose an estimated $11bn in export proceeds over the coming year.

Profile Who is Juan Guaidó? Show The opposition leader Juan Guaidó was almost unknown both inside and outside Venezuela until the start of this year. Guaidó was made chairman of the national assembly in January because it was the turn of his party, Voluntad Popular (People’s Will). At 35, he was a junior member of his party but its leaders were either under house arrest, in hiding or in exile. He declared himself "interim president" that month, resting his claim on a clause in the constitution that allows the legislature to take power temporarily and call new elections if it deems the president to be failing to fulfil basic duties or to have vacated the post. Guaidó's relative obscurity initially proved an advantage in a country where the opposition has generally failed to distinguish itself, losing its nerve at critical moments, succumbing to infighting, and getting involved in a failed coup against Hugo Chávez in 2002. He inspired a huge wave of protests inside Venezuela with a message of peaceful change, and won widespread international support. Countries from Europe to the US and regional powers recognised him as Venezuela's legitimate president, handing him control of bank accounts and Venezuelan assets along with the formal recognition. As months dragged on however, Guaidó's hope of winning a wave of military defections that would end the rule of Nicolás Maduro seemed to fade, leaving his movement in an uneasy limbo - self-declared president but with no power. He raised concerns inside Venezuela and internationally when he appeared to hint at the possibility of military intervention after a failed attempt to bring humanitarian aid into the country in February. Questions have also been raised about the bedfellows Guaidó has chosen in what he calls his bid to rescue Venezuela. His main international backer is Donald Trump.

Another key regional supporter is Brazil’s far-right firebrand president, Jair Bolsonaro, known for his hostility to human rights and his fondness for dictatorship. Despite these characteristics, Guaidó has praised what he called Bolsonaro’s “commitment to and for democracy [and] human rights”. Photograph: Luis Robayo/AFP

Bolton said the sanctions were an attempt to alleviate “the poverty and the starvation and the humanitarian crisis” gripping the South American nation and to stop “Maduro and his cronies” looting the assets of the Venezuelan people.

“Now is the time to stand for democracy and prosperity in Venezuela,” he said, calling on “all responsible nations” to back Guaidó.

John Bolton, the US national security adviser, holds a notepad with ‘5,000 troops to Colombia’ written on it. Photograph: Win McNamee/Getty Images

The notepad Bolton was holding as he took to the stage hinted at how potentially dangerous the situation could be. A handwritten note on its yellow pages appeared to read “5,000 troops to Colombia”.

Asked if there was any possibility of US troops getting involved in the Venezuelan crisis, Bolton replied: “Look, the president has made it very clear on this matter that all option are on the table.” On Monday, Bolton had warned that any violence against Guaidó, the Venezuelan opposition or US diplomatic staff “would be met by a significant response”.

Q&A Why is Venezuela in such a bad way? Show Venezuela’s current plight can be traced to a revolution that went terribly wrong. When Hugo Chávez, a former military officer, was elected president in 1998, he inherited a middle-income country plagued by deep inequality. Chávez had led an abortive coup attempt in 1992 and after winning power through the ballot box he set about transforming society. Chávez drove through a wide range of social reforms as part of his Bolivarian revolution, financed with the help of high oil profits – but he also bypassed parliament with a new constitution in 1999. The muzzling of parliamentary democracy – and the spread of corruption and mismanagement in state-run enterprises – intensified after 2010 amid falling oil prices. Chávez’s “economic war” against shortages led to hyperinflation and the collapse of private sector industry. The implosion in the economy between 2013 and 2017 was worse than the US in the Great Depression. In an attempt to stabilise the economy and control prices of essential goods, Chávez introduced strict controls on foreign currency exchange, but the mechanism soon became a tool for corruption. When Chávez died of cancer, his place was taken by his foreign minister, Nicolás Maduro, who has intensified his mentor’s approach of responding to the economic downward spiral by concentrating power, ruling by decree and political repression. Photograph: HANDOUT/X80001

Guaidó said he would offer amnesty to Venezuela’s military and extend it to Maduro, according to the television news network.

Guaidó also said he had spoken with Donald Trump a number of times, according to CNN. When asked about a possible military option in Venezuela, Guaidó said the US president had told him all options were on the table, CNN said.

The UN human rights office said security forces in Venezuela had detained nearly 700 people in one day last week amid anti-government protests – the highest such tally in a single day in the country in at least 20 years.

The UN spokesman Rupert Colville said on Tuesday that 696 people were detained on 23 January alone. Overall, 850 people were detained between Monday and Saturday, including 77 children.

Colville said more than 40 people were believed to have been killed “in different manners” in the recent protests, including 11 people reportedly killed by “unidentified individuals” linked to incidents of looting. He said one member of Venezuela’s Bolivarian national guard was reportedly killed in the state of Monagas.

He told reporters in Geneva that officials were investigating reports of ill-treatment of detainees.