President-elect Donald Trump took to Twitter on Tuesday night to say that a planned intelligence briefing for him on "so-called 'Russian-hacking'" had been delayed until Friday, a development he called "very strange!"

The tweet was the latest sign of Trump's skepticism about a case pressed by the Obama administration, based on the work of U.S. intelligence and law-enforcement agencies, that Russia tried to influence the U.S. presidential election by hacking Democratic email accounts, among other actions. Several leading Republicans have also endorsed that view.

Speaking outside a party at his Mar-a-Lago estate in Florida last week, Trump sounded dismissive of those assessments, saying it was "time for the country to move on to bigger and better things." But he indicated that he was willing to listen to a briefing on the issue this week.

Those remarks on Thursday came just hours after President Barack Obama announced retaliation against Russia that included the removal of 35 Russian government officials and other sanctions against state agencies and individuals allegedly tied to hacking.

In his tweet on Tuesday night, Trump speculated that the reason for the delay of his briefing until Friday was "perhaps more time to build a case."

"Very strange!" the president-elect said in the tweet.

Trump also spoke briefly to reporters on Saturday about the situation, saying that "no computer is safe" and that, for intelligence officials, "hacking is a very hard thing to prove."

"You want something to really go without detection, write it out and have it sent by courier," Trump said.

Trump also suggested at that time that he had additional knowledge to share about the situation, saying, "I also know things that other people don't know, and so they cannot be sure of the situation."

When asked what he knew that others did not, Trump demurred, saying only, "You'll find out on Tuesday or Wednesday."

For months, Trump has sounded skeptical about Russian responsibility for the hacks, which included the email accounts of the Democratic National Committee and John Podesta, the chairman of the campaign of Democratic nominee Hillary Clinton.

Trump has suggested other countries could be involved or that it could be the work of "somebody siting on their bed that weighs 400 pounds."