But what will it do after Sunday's presidential elections which it has denounced as a "sham"?
From more sanctions to a military intervention, analysts consulted by AFP examine the options for the US government:
The United States, which in March 2015 labelled Venezuela "a national security threat," has already imposed sanctions on dozens of officials and companies from the Socialist government in Caracas.
Maduro and several other senior government officials have been targeted and accused of corruption or complicity in drug trafficking.
President Donald Trump has also banned US entities from buying bonds from the Venezuelan state or from its oil company, PDVSA, and has forbidden any trading in the petro, the new crypto-currency that Venezuela launched to the public in March.
"If Maduro wins, as he is expected to, the US government will certainly tighten the screws even more," said David Smilde of the WOLA center for human rights in Washington.
Mariano de Alba, a Venezuelan lawyer who specializes in international affairs, said Washington will step up sanctions against Venezuelan government officials, "including their relatives and associates."
He said that similar steps would probably be taken by the European Union, Canada and other Latin American countries, at Washington's urging.
The US Treasury Department's sanctions list will likely be extended to include Maduro's powerful deputy Diosdado Cabello, said Jason Marczak, director of Latin American studies at the Atlantic Council, an independent think-tank.
"Trump will have little choice but to show greater toughness," said Michael Shifter, president of the Inter-American Dialogue which tries to foster democratic governance, after the US Ambassador to the United Nations, Nikki Haley, said last week it was "time for Maduro to go."
The Conoco effect
An oil embargo seems unlikely in the short term, said de Alba, especially since the US oil giant ConocoPhillips in April won a court order allowing it to seize $2 billion in PDVSA assets under an International Chamber of Commerce arbitration court ruling, a tough blow for Caracas.
"The Conoco situation is placing a huge burden on the Maduro government, because no Venezuelan oil tanker can leave to international waters without the threat of being seized," said Marczak.
Smilde agreed, but said that before Washington starts a total oil blockade, it can take intermediary measures against the Venezuelan oil sector -- the backbone of the failing economy -- such as putting sanctions on companies that insure Venezuelan tankers.
"A more drastic measure -- stopping oil imports from Venezuela -- now appears less likely, since that could exacerbate the country's humanitarian crisis, strengthen Maduro politically, and open the way for deeper Russian and Chinese involvement in Venezuela," said Shifter.
But the United States will want to avoid "external factors exacerbating an already incredible humanitarian crisis and causing more people to leave," said Marczak.
The military factor
Can the US military play a role in "restoring democracy" to Venezuela?
Trump said last August he was "not going to rule out a military option" in Venezuela.
His hawkish tone was applauded by some Venezuelan exiles in Miami.
"There is a clear risk of military action on the part of the United States," said Smilde. "Expat Venezuelans have been calling for it for some time, and there are always politicians and officials who are interested in military action."
"Although the administration repeatedly says 'all options are on the table,' US military intervention remains highly improbable," he said.
Marczak was also skeptical of any US military operations, but did not rule out a post-election deepening of the "disenchantment" felt in the ranks of the Venezuelan armed forces, who would have to decide whether to continue obeying the country's leader.
"There's potential for the post-election situation to get even worse," he said.
No 'coherent' policy
Washington is officially pushing moves to exert external pressure in the hopes that it will result in a peaceful internal solution in Venezuela, a strategy set out by Vice President Mike Pence at a meeting of the Organization of American States last week.
But Richard Feinberg of the Brookings Institution said there was little evidence of "a coherent, workable policy" on Venezuela in Washington.
"I think the Trump administration's rhetoric on Venezuela, as on Cuba, is more oriented toward pleasing the respective exile communities than toward obtaining real results on the ground in those countries," he said.
"Any post-May 20 elections reaction will be purely ad hoc and unlikely to have a decisive impact on events," he said.
Victoria Gaytan, of the Global Americans working group on inter-American relations, did expect more pressure from Washington after Sunday's polls, not just from Washington but from the international community in general.
Measures could include a refusal to acknowledge the election results, more economic sanctions and the denial of visas to Venezuelan officials.
"What we can expect to see is a stronger commitment by the international community and from the region," she said.