(CNN) President Donald Trump signaled on Tuesday he's prepared to dismiss aides with whom he's clashed -- including national security adviser H.R. McMaster -- as he works to surround himself with advisers more aligned with his populist agenda and freewheeling style.

Inside the West Wing, McMaster appeared poised to soon depart following months of speculation about his standing, people familiar with the matter said.

The shakeups come as Trump enters the second year of his presidency buoyed by economic successes but weighed down by external distractions like the Russia investigation and ethics blunders by members of his Cabinet.

Outside advisers to the President have also felt out potential candidates to replace chief of staff John Kelly, a person who has been approached about the position tells CNN. Kelly's departure is seen as less imminent than McMaster's, and Trump publicly praised his chief of staff on stage in California on Tuesday.

Trump has grown irritated with his embattled Veterans Affairs Secretary David Shulkin and is now making plans to remove him from his post, two sources familiar with the move told CNN . He's eyed Energy Secretary Rick Perry as a possible replacement, a person familiar with the matter said.

Earlier, Trump told reporters at the White House he was nearing his staffing ideal

"I'm really at a point where we're getting very close to having the Cabinet and other things that I want," Trump told reporters on the South Lawn on Tuesday, moments after announcing he was ousting Secretary of State Rex Tillerson

A senior administration official said a further shake-up of senior staff could happen as soon as this week. Other officials suggested a longer timeline, saying Trump could execute changes over the course of the next two months.

The White House didn't respond on Tuesday when asked about McMaster's standing, and last week press secretary Sarah Sanders said only that "the President's national security adviser is General McMaster."

"He's a valued member of the President's team and an important part of this process," Sanders said on Friday.

Time is running short

Inside the White House, speculation has mounted that McMaster's time is running short. But the timing of any potential departures has been tightly held, leading to a sense that Trump could tweet at any moment -- without forewarning -- to make personnel changes.

A spokesman for the National Security Council did not immediately respond to a request for comment.

Aides highlighted Trump's mention on Tuesday of Tillerson's opposition to scrapping the Iran nuclear deal, a position he shared with McMaster. McMaster helped develop the plan unveiled last year that punted the Iran deal to Congress. Like Tillerson, he has been opposed to withdrawing the US from the plan, but has pressured European allies to make changes to the agreement brokered during the Obama administration.

Current candidates under consideration to replace McMaster include Bolton, the former US ambassador to the United Nations under President George W. Bush; Oracle executive Safra Catz; National Security Agency Director Admiral Mike Rogers; and Stephen Biegun, a vice president at Ford Motors and a former senior staff member in the George W. Bush administration.

Bolton has met personally with the President several times, including during an Oval Office meeting last week. He has maintained his heavy presence on Fox News over the past week, including over the weekend and last night, praising Trump's decision on North Korea and even encouraging a speedier timeline for talks with Kim Jong Un.

Kelly watch

Meanwhile, some allies of the President have begun identifying potential replacements for Kelly, whose strict management style has clashed with Trump's more freewheeling preferences. It's not clear, however, that Trump himself has held formal conversations with possible chief of staff candidates.

Officials said there is no solid sense of how long Kelly will last in the West Wing, where he's brushed up against members of Trump's family, including Jared Kushner and Ivanka Trump. Kelly traveled with Trump on Tuesday to California, and was by the President's side for most of the day as he toured prototypes for a border wall.

Trump hailed his top aide during remarks to US service members at a Marine Corps base outside San Diego, saying the retired Marine general is "doing a great job in Washington."

But he suggested Kelly preferred life in the military.

"I think he likes what you do better than what he does, but he's going a great job. He misses you," Trump said.

Shulkin in quicksand

Shulkin's standing in the administration has been in quicksand for weeks now as his agency devolves into turmoil, and though the White House press secretary maintained just last week that he has done "a great job," Trump now wants him out.

Trump and his senior aides are frustrated with Shulkin because they believe he has undermined the White House on several occasions and is unwilling to work with other members of his agency who were appointed by the Trump administration, a source familiar tells CNN.

His status as the sole Obama holdover in Trump's administration initially did not raise any issues, people familiar with the situation said. But the events of recent weeks made clear to Trump and his associates the importance of naming their own person to the job.

Trump and Perry discussed a possible move during their lunch at the White House Monday.

A Shulkin adviser referred questions about this report to the White House. The White House declined to comment. An Energy Department spokeswoman, asked about reports Perry is being eyed to replace Shulkin, said: "I have no comment at this time."

The President's strong preference is to announce any new departures only once replacements have been selected, as he did Tuesday when he named CIA Director Mike Pompeo as Tillerson's replacement.

The outgoing chief economic adviser Gary Cohn angered the White House when he announced his resignation before Trump had selected his successor. Cohn was frustrated by the President's decision to impose tariffs on foreign imports of steel and aluminum, a move he opposed.

On Tuesday, Trump suggested that economist and CNBC commentator Larry Kudlow was his top choice to replace Cohn, confirming reports that he'd all but made his decision.

"I'm looking at Larry Kudlow very strongly," Trump said. "I've known him a long time. We don't agree on everything but in this case I think that's good. I want to have a divergent opinion."