Venezuelan President Nicolas Maduro celebrates the results of Constituent Assembly, in Caracas, on July 31, 2017. (Xinhua/AFP Photo)

WASHINGTON, Aug. 1 (Xinhua) -- Though U.S. sanctions on Venezuelan President Nicolas Maduro were seen by many as symbolic, more U.S. sanctions targeting the country could follow, experts said.

The United States on Monday slapped economic sanctions on Maduro after Venezuela held its National Constituent Assembly (ANC) on Sunday.

"By sanctioning Maduro, the United States makes clear our opposition to the policies of his regime," U.S. Treasury Secretary Steven Mnuchin said in a statement.

Though it was rare for the United States to slap sanctions on a sitting leader of a country, the U.S. move on Monday was far more limited in its scope compared to previous estimation that the United States would target Venezuela's oil industry.

Venezuelan political observer Sergio Rodriguez Gelfenstein told Xinhua that the U.S. sanctions against Maduro were a symbolic measure designed to show Washington's disapproval of the leader who defied a White House order to scrap Sunday's poll.

Personal sanctions against Maduro are unlikely to harm U.S. interests, whereas economic sanctions against the South American country could affect U.S. businesses, Rodriguez said.

"Maduro is not going to be deterred, so the question is what happens when the new constituent assembly starts dismantling the existing institutions or we have further bloodshed. I think we will start to see escalating economic measures," Helima Croft, head of commodity strategy at RBC Capital Markets, told CNBC.

Maduro on Monday rebuffed U.S. sanctions that targeted him personally, saying he was "proud" to be singled out by the measure.

"They sanction me because I call for an electoral process that is unique in the history of the Americas ... because I don't obey the orders of foreign governments? If that is so, then I feel proud of the proposed sanction," said Maduro.

"The threats and sanctions ... do not intimidate me... I have nothing to fear," Maduro said, adding that the sanctions serve to highlight the impotence, desperation and hatred felt in Washington.

Apart from the sanctions against Maduro, the U.S. Treasury Department had slapped sanctions on 13 current or former senior officials of the Venezuelan government amid political turmoil in the South American country.

The U.S. Treasury Department on Monday also warned that anyone who participates in the ANC could be exposed to future U.S. sanctions.

Currently, the Trump administration is keeping all sanctions options on the table.

According to White House senior officials who briefed reporters on Venezuela sanctions, possible sanctions on Venezuela's oil sector were also considered.

"All options are being carefully studied, carefully analyzed," said the official on a conference call last week.

Among the possible U.S. sanctions on Venezuela, the most severe option would be an embargo against Venezuelan crude oil imports into the United States.

According to data by U.S. Energy Information Administration, Venezuela is the third biggest U.S. supplier of oil.

Given the fact that Venezuela's oil industry supplies over 90 percent of the South American country's hard currency, such a U.S. embargo would further cripple Venezuela's already weak economy.

The Wall Street Journal cited sources familiar with White House inner discussion on Venezuela sanctions as saying that an embargo against Venezuelan crude oil imports into the United States was currently off the table.

The most likely option is a ban on exports to Venezuela of refined petroleum products and lighter crude grades that Venezuela mixes with the heavy crude it then sells to the United States, say the people familiar with U.S. discussions.

That could force Venezuela to import light crude at higher prices from distant places like Algeria or Nigeria, and deepen its steady oil output decline, Francisco Monaldi, a Venezuela expert at Rice University, told The Wall Street Journal.

Another option is to ban state oil company Petroleos de Venezuela from using the U.S. banking system and U.S. currency, the people were quoted as saying.

The vote on Sunday came at a time of high tensions in Venezuela, with anti-government protests organized by the opposition having led to more than 110 deaths since early April.