US President-elect Donald Trump says he is willing to work with Russia and China, providing they cooperate.

Mr Trump told the Wall Street Journal that newly-imposed sanctions on Russia would remain "at least for a period of time" but could then be lifted.

He also said the One China policy, in which the US no longer acknowledges Taiwan, was up for negotiation.

Meanwhile, a US Senate committee will probe claims Russia attempted to meddle in the presidential election.

In his interview, Mr Trump said sanctions on Russia could be lifted if Moscow helped Washington in the war against Islamic extremism and in other matters.

"If you get along and if Russia is really helping us, why would anybody have sanctions if somebody's doing some really great things?"

He said he hoped a meeting with President Vladimir Putin would be arranged.

With regards to Beijing, Mr Trump said China had to allow US companies to compete by floating its currency.

But he said he would not label China a currency manipulator the instant he took office.

He had already questioned the One China policy last month, provoking angry responses in Chinese state media.

'Full understanding'

Republican and Democratic leaders on the Senate Intelligence Committee vowed to follow their investigation "wherever it leads".

They will examine Russia's cyber activity and intelligence practices.

Interviewees will include members of the current US administration and President-elect Donald Trump's team.

A statement, released by the committee late on Friday, said: "We believe that it is critical to have a full understanding of the scope of Russian intelligence activities impacting the United States."

The committee will examine whether there were any contacts between Russia and people associated with the US political campaigns.

It said subpoenas would be issued "if necessary to compel testimony".

The bulk of the work will be done behind closed doors, although the senators say they will hold open hearings when possible.

"The committee will follow the intelligence wherever it leads. We will conduct this inquiry expeditiously, and we will get it right," said the statement.

The senators said they would produce both classified and unclassified reports on their findings.

Earlier this week, details emerged of an unproven dossier alleging that Russian security officials have compromising material on Mr Trump, which could make him vulnerable to blackmail.

The US president-elect said the claims were "fake news" and "phoney stuff".

He announced that his team would produce its own "report on hacking" within 90 days.

The US released an unclassified intelligence report earlier this month, claiming that Russian President Vladimir Putin had ordered the hacking of Democratic Party emails to damage Mr Trump's Democrat rival, Hillary Clinton, and influence the election.

It also said Russia had used state-funded propaganda and paid social media users, or "trolls", to launch online attacks.

In December, US President Barack Obama expelled 35 Russian diplomats from the country in response to the hacking allegations.

Russia says allegations that it ran a hacking campaign to influence the US presidential elections are "reminiscent of a witch-hunt".