By Clare Foran and Manu Raju, CNN

(CNN) -- The White House called Democratic Sen. Joe Manchin after Vice President Kamala Harris conducted interviews with West Virginia media, according to a person with knowledge of the conversation.

The outreach comes after Harris' apparent move to apply pressure on Manchin frustrated the conservative Democrat, something that he made clear over the weekend.

The source declined to say what the White House said to Manchin or who from the White House called him, but the call underscores the delicate balancing act President Joe Biden faces as he and Democrats try to hold a narrow Senate majority together to pass a sweeping Covid relief plan -- and any other legislation this year.

The Senate's 50-50 partisan split gives the White House little room for error and Manchin will be a key vote on any package.

"We've been in touch with Sen. Manchin, as we have been for many weeks and will continue to be moving forward," White House press secretary Jen Psaki said on Monday.

"Not only is he a key partner to the President and to the White House on this package, but on his agenda and we will remain in close touch with him," she added.

Psaki did not say who in the White House had spoken to Manchin following his comments about Harris' interviews. Asked specifically whether Biden himself had spoken to the senator, Psaki demurred, saying only the White House had been in touch.

Manchin appeared to express frustration over a television interview Harris recently did in his home state to promote the American Rescue Plan last week.

In an interview with CNN affiliate WSAZ in West Virginia, Manchin bristled at Harris' interview with the same station that took place on Thursday, suggesting the administration did not give him a heads up.

"I saw it. I couldn't believe it. No one called me," he said. "We're going to try to find a bipartisan pathway forward. I think we need to, but we need to work together. That's not a way of working together, what was done."

On Thursday, Harris promoted the $1.9 trillion Covid relief plan in interviews with television stations in West Virginia and Arizona -- states that are home to Democrats whose votes could be critical to passing Covid relief, including Manchin in West Virginia and Sen. Kyrsten Sinema, along with Sen. Mark Kelly, who will face re-election in the state in 2022, in Arizona.

In an interview with WSAZ Thursday, Harris said she and Biden believe it's important to "work with a sense of urgency" to address the public health and economic crisis. The Vice President touted the package, saying it's "about opening schools back up in a safe way, it's about getting support for small businesses, getting relief for families."

Harris also spoke about the economic situation of the West Virginia coal industry.

"All of those skilled workers who are in the coal industry and transferring those skills to what we need to do in terms of dealing with reclaiming abandoned land mines; what we need to do around plugging leaks from oil and gas wells; and, transferring those important skills to the work that has yet to be done that needs to get done," she said.

Psaki declined to say on Monday whether Harris' interview was designed specifically to apply pressure on Manchin.

"Our focus is communicating with the American people about how the American rescue plan can help put food on the table, can help ensure we can get vaccines in the arms of Americans and help send kids back to school," she said. "That's our overarching objective with all of the communications we do."

This story has been updated with comment from the White House.