The White House is once again facing a crisis over its links to the Kremlin, after it emerged that Donald Trump met the Russian ambassador during his election run last April. Trump and his aides have previously strongly denied that the president had any contact with Russia during his campaign.

Having already seen his first choice for national security adviser resign over his contact with Russian ambassador Sergey Kislyak, and his attorney general recuse himself from any investigations into links with Russia, Trump is now directly in the firing line — not because of the meeting itself but because of his repeated denials.

“Russia is a ruse. I have nothing to do with Russia. Haven’t made a phone call to Russia in years. Don’t speak to people from Russia,” Trump said at a press conference just last month.

While not denying that an encounter took place, a White House official called the reports of a scheduled meeting “disingenuous and absurd.”

Here’s what you need to know:

A Wall Street Journal report published May 13 last year described Trump delivering a foreign policy speech at the Mayflower Hotel in Washington, D.C., on April 27 in which he said an “easing of tensions and improved relations with Russia” was possible. Russia was apparently happy with the content of the speech.

The report went on to say, “A few minutes before he made those remarks, Mr. Trump met at a VIP reception with Russia’s ambassador to the U.S., Sergey Ivanovich Kislyak. Mr. Trump warmly greeted Mr. Kislyak and three other foreign ambassadors who came to the reception.”

Such a meeting is not unusual. Many foreign ambassadors seek to meet candidates from both sides during election campaigns and report back to their governments about any potential impact on foreign policy.

What is unusual is the fact that Trump and his administration have made categoric denials that the president had any contact with Russian government officials during the campaign.

As well as Trump’s own denial last month, here’s what deputy White House press secretary Sarah Sanders told reporters just last week: “The big point here is the president himself knows what his involvement was, and that’s zero. And I think that he’s the primary person that should be held responsible, and he had no interaction, and I think that’s what the story should be focused on.”

Kislyak has been at the center of almost all the controversy surrounding the Trump administration’s links to Russia in recent months. Michael Flynn was forced to resign as national security adviser after it emerged he misled White House officials — including Vice President Mike Pence — on the content of his discussions with Kislyak prior to taking office.

Last month it came to light that Attorney General Jeff Sessions had met with Kislyak twice during the election campaign. Sessions had denied that such meetings took place during his Senate confirmation hearing. Despite loud calls for his resignation, Sessions remains in office but promised to recuse himself from any investigation of the Trump campaign’s contacts with Russia.