President Reagan has not decided whether to lift the Soviet grain embargo or to seek decontrol of natural gas by Sept. 30, White House deputy press secretary Larry Speakes said yesterday.

As he left a presidential prayer breakfast Reagan was asked about a Washington Post article saying that the embargo would be continued for the foreseeable future. "No decision has been made," he replied.

Sen. Bob Dole (R-Kan.), a strong opponent of the embargo, said yesterday that he thinks the president will lift it. "In my view, he made a campaign promise to remove it, to lift the embargo," Dole said.

The president has promised Dole and other anti-embargo senators from farm states that he will not make a decision on the embargo at least until after Feb. 17, when he will meet with them and listen to their arguments in favor of ending the embargo, imposed by former president Carter after the Soviet invasion of Afghanistan.

Senate Majority Leader Howard H. Baker Jr. (R-Tenn.), meanwhile, said that a turnaround on the issue would not embarrass Reagan. Conditions change, Baker said. "It would be foolhardy to say . . . positions you take in the campaign must never be varied."

The grain embargo was discussed during a Wednesday Cabinet meeting and will be discussed further at another Cabinet-level meeting, according to White House press secretary James S. Brady.

On decontrol of natural gas, Speakes told reporters that "no final decisions have been made and won't be for a number of days."

He indicated, however, that a decision on decontrol of natural gas would be made in the near future.

Baker said he favors decontrol, but would also favor imposition of a windfall profits tax, "at least a temporary one," to accompany decontrol.