Minister K Natwar Singh may be running out of options with Prime Minister Manmohan Singh not ruling out the possibility of appointing an External Affairs Minister during the Cabinet expansion he plans to undertake after the Parliament session. While confirming that he was looking at a possible Cabinet expansion after the winter session, the PM, who left for Moscow today on a three-day visit, hinted that the option of appointing a Foreign Minister was not a shut case. ‘‘As of now, I have still not made up my mind on that,’’ he said, thereby indicating that the matter was under consideration. Natwar Singh had to give up the External Affairs portfolio in the wake of the Volcker Committee revelations last month. The ministry was brought under the PM while Natwar retained his Cabinet rank without a portfolio. This gave the impression that Natwar might be brought back to the ministry in case investigations gave him a clean chit. But fresh confirmation about the oil deal by Natwar’s old confidante Aneil Mathrani has reduced this possibility. Not keen on speaking at length on the issue after having made a statement in Parliament, Singh refused to get drawn into speculation on Natwar voluntarily resigning from the Cabinet. ‘‘If a person takes a decision voluntarily, and such a situation arises, then we will consider what to do.’’ The PM had met Natwar Singh on the latter’s request on Saturday. In their 40-minute meeting, Singh said Natwar discussed with him developments in the past two weeks, indicating that the storm over Mathrani’s revelations did come up in the meeting.