President Carter has scheduled meetings with his senior White House staff and Cabinet today, amid widespread speculation he will move soon to carry out his promised restructuring of the top levels of his administration.

One informed source said that elements of the staff reorganization may be announced to the senior staff at 9:30 this morning, but that decisions about Cabinet members are probably still some away.

The one seeming certainly in the reorganization is an explicit expansion of the authority of Hamilton Jordan, Carter's 1976 campaign manager, into something approximating a chief of the White House staff.

Jordan, an assistant to the president, has served as staff coordinator on such major projects as the ratification of the Panama Canal and SALT II pacts. But his authority over other staff members has been limited by Carter's insistence that he did not want any single aide to have the broad authority that H. R. (Bob) Haldeman had exercised in the Nixon White House.

But with Carter confessing at the end of his 10-day stay in Camp David that he had allowed himself to become too bogged down in the details of decision-making, to the detriment of his role as a natioal leader, there appears little doubt that he is already for a devolution of authority to his aides.

Some of those who conferred with the president during his stay at Camp David predicted yesterday that the staff reshuffle could also involve a new role for White House press secretary Jody Powell.

One possibility was that Powell would team Jordan, with Jordan coordinating White House staff activities and Powell working to ensure that the president's directives are followed in the departments and agencies.

But that report could not be confirmed and was challenged as unlikely by some Carter aides.

One member of the senior staff summed up the situation last night by saying: "Whatever decisions have been made, they're being very tightly held." Most - if not all - of the people who would be most affected by the staff reshuffle plainly were in the dark.

But Jordan is known to have submitted his recommendations to the president last week and others who met the president at Camp David said they are sure Carter is going to move quickly to deliver on his promise to clarify lines of authority in his official family.

There was less certainty about Carter's intentions with regard to his Cabinet. In briefing journalists last Friday at Camp David, Carter said he intends to make some basic changes in both the Cabinet and staff structures.

Prior to the Camp David meetings, Carter repeatedly had expressed his satisfaction with the entire Cabinet and said he hoped and expected all of its members to serve with him at least until the end of this term.

But visitors to Camp David said the president had heard repeated suggestions that at least three of the most important Cabinet members - Secretary of Energy James B. Schlesinger, Secretary of Health, Education and Welfare Joseph A. Califano, Jr., and Secretary of Treasury W. Michael Blumenthal - were either political liabilities or were causing trouble by their independence from White House direction.

Schlesinger, who is also a target of criticism on Capitol Hill, reportedly was defended by the president in the Camp David talks. But there have been authoritative reports that the energy secretary wants to leave the Cabinet before the 1980 campaign begins, because he thinks he may be a political liability to the president.

Califano's and Blumenthal's standing with the president is unknown. Both have been frequent targets of criticism at the staff levels of the White House, but Carter exphasized Blumenthal's role as coordinator of administration economic policy as recently as last month.

Visitors to Camp David said that two other Cabinet members - Secretary of Transportation Brock Adams and Secretary of Housing and Urban Development Patricia R. Harris - also were "put on the pan" by some of the invited guests. But there was no indication that their jobs were in jeopardy.

Carter added to the speculation about Cabinet changes by saying in his Sunday night address that he had been told that "some of your Cabinet members don't seem to be loyal." By leaving the statement unchallenged he appeared to accept it as valid.

One adviser to the president cautioned, however, that Carter's ability to change his Cabinet may be limited, not just by his personal reluctance to fire appointees, but by the difficulty of recruiting new people of stature this late in the administration's life. Facing a fight for renomination and reelection, Carter can promise a new Cabinet memberbarely a year of effective service at this point

However, almost all who discussed the basic structure of the administration with the president came away convinced that Carter will "reach out for help," as one man said, by expanding the White House staff and probably changing faces in the Cabinet as well. CAPTION: Picture, HAMILTON JORDAN . . . expected to gain added authority