Jared Kushner, the president’s son-in-law and senior adviser, was looking for a direct line to President Vladimir Putin of Russia — a search that in mid-December found him in a room with a Russian banker whose financial institution was deeply intertwined with Russian intelligence, and remains under sanction by the United States.

Federal and congressional investigators are now examining what exactly Mr Kushner and the Russian banker, Sergey Gorkov, wanted from each other.

The banker is a close associate of Mr Putin, but he has not been known to play a diplomatic role for the Russian leader.

That has raised questions about why he was meeting with Mr Kushner at a crucial moment in the presidential transition, according to current and former officials familiar with the investigations.

The New York Times first reported the meeting between Mr Kushner and Mr Gorkov in March, but the White House at the time did not explain its aim.

That article quoted White House spokeswoman Hope Hicks, who said that the meeting came at the request of the Russian ambassador to the United States, Sergey Kislyak, with whom Mr Kushner had met earlier in December at Trump Tower to discuss opening a communications channel with Russian officials during the presidential transition.

But the half-hour meeting with Mr Gorkov since has come under increasing scrutiny. The current and former American officials now say it may have been part of an effort by Mr Kushner to establish a direct line to Mr Putin outside of established diplomatic channels.

The meeting came as Mr Trump was openly feuding with American intelligence agencies and their conclusion that Russia had tried to disrupt the presidential election and turn it in his favour.

The Senate Intelligence Committee notified the White House in March that it planned to question Mr Kushner about the meeting.

On Friday, citing American officials briefed on intelligence reports, The Washington Post reported that Mr Kislyak told his superiors in Moscow that Mr Kushner had proposed a secret channel and had suggested using Russian diplomatic facilities in the United States for the communications.

The White House has not denied the Post report, which specified that Russian communication centres at an embassy or consulate in the United States were discussed as hosts for the secure channel.

Several people with knowledge of the meeting with Mr Kislyak said the secure channel, in part, sought to connect Michael Flynn, a campaign adviser who became Mr Trump’s first national security adviser, with military officials in Moscow.

Mr Flynn attended the meeting at Trump Tower with Mr Kislyak.

During the Trump administration’s first week, administration officials said they were considering an executive order to unilaterally lift the sanctions, which bar Americans from providing financing to and could limit borrowing from Mr Gorkov’s bank, Vnesheconombank.

Removing the sanctions would have greatly expanded the bank’s ability to do business in the United States.

In a statement on Monday, Ms Hicks said that “Mr Kushner was acting in his capacity as a transition official” in meeting with the Russians.

Mr Kushner has agreed to be interviewed by congressional investigators about the meetings, she said.

At the time of the meeting, Mr Kushner was still running the company, which is his family’s real estate business.

Vnesheconombank has not responded to questions about which other financial institutions and business leaders Mr Gorkov met with while in the United States.

Trying to set up secret communications with Mr Putin in the weeks after the election would not be illegal.

Mr Kushner disclosed none of his contacts with Russians or any other foreign officials when he applied for his security clearance in January. He later amended the form to include several meetings, including those with Mr Kislyak and Mr Gorkov, but it is unclear whether he told the investigators who conducted his background check about the attempts to set up a back channel.

His aides have said his omissions from the clearance form were accidental.

The meeting with Mr Gorkov is now being scrutinised by the FBI as part of its investigation into alleged Russian attempts to disrupt last year’s presidential campaign, and whether any of Mr Trump’s advisers assisted in such efforts.

Vnesheconombank has been used by Russian intelligence to plant spies in the United States. In March 2016, an agent of Russia’s foreign intelligence service, known as the SVR, who was caught posing as an employee of the bank in New York, pleaded guilty to spying against the United States.

The spy, said Preet Bharara, then the United States attorney in Manhattan, was under “the guise of being a legitimate banker, gathered intelligence as an agent of the Russian Federation in New York”.

– The New York Times