(CNN) Republican Sen. Chuck Grassley, who for days has urged the White House both publicly and privately not to fire a top immigration official, said Wednesday he hasn't received any assurances his efforts will work -- and will have to accept it if they do not.

"I've concluded that they're taking it under consideration," Grassley told reporters of his efforts to keep Lee Francis Cissna in his job as the top official at the US Citizenship and Immigration Services. "I don't know whether I'll be satisfied or not when it's all done, but I'm beyond the point of considering whether or not I'm going to be satisfied."

It has been made clear on Capitol Hill that White House frustration with the agency has put its chief in danger of being the latest of a series of officials inside the Department of Homeland Security to be fired.

The talk of Cissna's departure has coincided with the resignations , or withdrawn nominations, of the Homeland Security secretary, acting deputy Homeland Security secretary and nominee to head the Immigration and Customs Enforcement, as President Donald Trump and top advisers have moved to dramatically shift the direction of DHS to a harder line on immigration.

Administration officials have made clear they are unhappy with how United States Citizenship and Immigration Services has handled elements of a surge of migrant apprehensions at the southern border in recent months, as well as the agency's pace in drafting regulations.

A powerful committee chairman and the most senior Republican in the chamber, Grassley's word, particularly given how public his objections to any dismissal of Cissna, carries significant weight on Capitol Hill. There's also been an even more robust effort behind the scenes. Grassley said he has personally spoken to "two or three people at the highest levels" of the White House, and that his staff has also backchanneled with White House officials in an effort to protect Cissna. Grassley said he hasn't spoken directly to the President.

"I spoke about the competence of people I know," Grassley said of his message to White House officials.

For Grassley, it's both personal and policy related -- Cissna worked for the Iowa senator when Grassley chaired the Judiciary Committee. But beyond that, Grassley has said he views Cissna as a competent official who can help the Trump achieve his goals -- goals Grassley said he shares. But he also appeared resigned to the fact that the decision was out of his hands.

"I know the President's goals on immigration are the same as mine, pretty much the same as mine I would say, and that the President's gotta have people in place who will do his job and since his goals are the same as mine I'm gonna have to accept it," Grassley said.

Grassley, in a separate conversation with reporters, did say he was "assured the (Cissna's) going to still be working at the Department of Homeland Security," but he did not elaborate on in what capacity that would entail.