Media mogul Rupert Murdoch took to Twitter on Saturday to savage the Obama-Biden campaign, appearing to throw his full support behind Mitt Romney little more than three weeks from election day.

Murdoch accused Vice President Joe Biden of lying about the administration's relationship with Israeli leader Benjamin Netanyahu, and of also not telling the truth about last month's deadly attack on the US consulate in Libya.

"Nightmare for Israel if Obama wins. Biden outright lied about personal relations with Bibi. Susan Rice for State real nightmare," Murdoch wrote on the microblogging service.

Rice, the US ambassador to the United Nations, has been mentioned as a possible successor to Secretary of State Hillary Clinton, who said she will leave her post after the November 6 election.

In the second of four tweets reeled off within 18 minutes, Murdoch lambasted President Barack Obama and his aides for their handling of the aftermath of the Benghazi consulate attack that killed four Americans including ambassador Chris Stevens.

"White House still lying about Benghazi. HAD to know truth, or is whole admin a shambles? Biden threw CIA under bus, now WH throws State!" he wrote.

Having earlier posted that he thought the 2012 race would come down to Ohio, one of 10 key swing-states, Murdoch noted the "huge spending by both sides," during the campaign, adding: "Obama tv buying operation infinitely smarter."

Murdoch, the News Corporation boss whose empire includes Fox News and The Wall Street Journal, has previously criticized the Romney campaign but his latest tweets make it clear that he wants Obama ousted from the White House.

"Next debate Romney needs to ignore personal attacks and pivot to plans for millions of jobs and real opportunity for all. Only that matters," he advised the Republican candidate.

Murdoch's criticism of Biden follows the vice president's remarks during a debate on Thursday, when the Democrat said Obama's relationship with Israel was strong.

Biden also said "with regard to Bibi, he's been my friend for 39 years."

Political bloggers have since pointed out that Biden has probably not known Netanyahu that long, as the latter was serving in the Israeli military and fighting in the Yom Kippur war in 1973.

The State Department has faced a media battle in recent weeks regarding its response to the Benghazi attack, which administration officials insist has been politicized by Republicans.

Murdoch's remarks about Rice may refer to a television interview the diplomat gave on September 16, just days after the the US deaths in Libya.

Rice said that, based on the information American officials had at the time, the incident appeared to be sparked by a "spontaneous" protest over an anti-Muslim film made on US soil and posted on YouTube.

But subsequent evidence suggested there was no major demonstration outside the consulate, and that the attack was planned by local militants, possibly with help from several outside extremists.

The State Department and the White House later admitted that the Benghazi attack was terrorism.

Murdoch, who in the United States and perhaps even more so in Britain is known for his willingness to switch political sides at opportune moments to ensure he backs election winners, has not always complimented Romney's efforts.

In July, after meeting Romney, the media baron tweeted that he doubted whether the Republican candidate could beat Obama.

But Romney has since revived his campaign and boosted his poll ratings, largely on account of a strong performance in the first of three televised debates against Obama.

Murdoch followed up a couple of hours later to offer a skeptical view on China.

"China in crisis. Massive public anger at corruption. Maybe change on way. Nobody can make confident predictions," he tweeted.