Saudi Arabia and other oil-rich Persian Gulf countries are hoping for Hillary Clinton to become the next US president, according to an oil analyst.

“It is no secret that the Saudis and other [Persian] Gulf Sunni powers are rooting for Mrs. Clinton,” Bob McNally, president of Washington-based consulting firm Rapidan Group, told CNBC from Vienna on Thursday.

The Organization of the Petroleum Exporting Countries (OPEC) holds its semiannual meeting Thursday in Vienna, but is unlikely to announce any strategy changes.

McNally said that there is “a lot of concern and anxiety” about what a Donald Trump presidency would mean for the oil market.

Trump, the presumptive Republican nominee, has questioned the protective nature of the US relationship with Saudi Arabia.

He has suggested that the United States should consider ditching Riyadh because Washington is increasingly getting less dependent on overseas oil.

The billionaire businessman laid out his energy plan for the US at an oil industry conference in North Dakota last week, where he called for complete independence from overseas oil imports, more fossil fuel drilling and fewer environmental regulations.

“America's incredible energy potential remains untapped. It's a wound that is totally self-inflected,” Trump said at the conference.

Kevin Cramer, a Republican congressman from North Dakota and a Trump adviser, recently urged the White House hopeful to criticize OPEC for manipulating oil prices.

Donald Trump speaks during a press conference at the Trump Tower on May 31, 2016 in New York. (AFP photo)

Trump had asked Cramer to suggest energy policies before the speech.

Trump became the presumptive Republican nominee in May after his two remaining rivals, Texas Senator Ted Cruz and Ohio Governor John Kasich, dropped out of the race following their crushing defeats in Indiana.

Last week, Trump won the support of enough unbound delegates to reach the 1,237-delegate threshold needed to clinch the nomination.

The former reality TV star is increasingly eating into Clinton’s national lead, according to recent polls.