The US government could announce new sanctions to pressure Venezuelan President Nicolas Maduro as early as next week unless his military defies orders to block convoys of humanitarian aid planned for this weekend, a senior administration official said on Friday.

US Vice President Mike Pence and other leaders in the Western Hemisphere will meet in Bogota on Monday. Depending on what happens on Venezuela's borders over the weekend, the leaders could dramatically boost aid pledges to the country - or take new steps to crack down, the official told reporters.

"If there is any type of violence, or if there is any type of negative reaction from the hierarchy of the Venezuela armed forces, there may also be measures that are announced by the vice president and other countries in regards to closing even further the international financial circle," the official said, speaking on condition of anonymity.

In a sign of the importance of the issue to the White House, President Donald Trump's top national security adviser John Bolton canceled a weekend trip to South Korea to talk to allies ahead of a summit next week on North Korea's nuclear talks.

Bolton wanted to monitor the unfolding developments in Venezuela, his spokesman Garrett Marquis said.

Pence will lead the US delegation to the meeting of the Lima Group regional bloc, and so far has an "open script" for what he will propose, the official said.

"He has the carrots, but he's also ready with the sticks for those that promote or execute violence," the official said. "That will be announced not only by the United States, but by the rest of the region's democracies."

The United States has stockpiled aid on Colombia's border with Venezuela at the request of opposition leader Juan Guaido, whom Washington and other dozens of other Western governments have recognized as Venezuela's legitimate president since Maduro held elections last year decried as fraudulent.

Despite shortages of food and medicine, Maduro has denied there is a crisis in the country, and says the aid is aimed at undermining his government. He has ordered some of the country's borders closed to keep the aid from entering.

Tensions are running high and there has been some violence. Soldiers killed two people and injured 15 near the border with Brazil on Friday, witnesses said.

The Trump administration last month slapped sanctions on state-owned oil company Petroleos de Venezuela PDVSA.UL, known as PDVSA, to cut Maduro off from his government's main source of revenues.

The administration official declined to comment on future sanctions, but said the United States and other allies are looking at ways to expel family members of Venezuelan military officials who are living outside the country - including some in south Florida.

"They're going to face a situation where they and their families are going to have to go back to Venezuela," he said.

The US official described the aid convoys as a key test for the Venezuelan military as its leaders weigh whether to obey Maduro or Guaido, who has asked the military to let it pass.

"It's really the first order he gives to them as their commander in chief," the US official added.