Egyptian Prime Minister Mustapha Khalil left for Washington today to meet President Carter and open what Egypt hoped will be the final phrase of the Middle East peace negotiations.

He was carrying a message detailing Egypt's views on the remaining issues. By all accounts, these differ only in nuance, not in substance, from demands already made public by Egyptian negotiators - a timetable for the Palestinian autonomy envisioned in the Camp David agreements an re-writing of an article in the draft treaty that would override Egypt's mutual defense commitment to the other Arabs.

Khalil departed after final round of discussions with President Anwar Sadat and Vice President Hosni Mobarak. The message he is carrying was worked out over several days of deliberations among these men and the Egyptian delegation to the Blair House talks.

The Egyptians have avoided saying their position is final. On the contrary, they have been stressing they want to negotiate. Foreign Ministry officials say this implies flexibility in the Egyptian position, provided a timetable is established for Palestinian home rule elections.

What the Egyptians have done is move their positions on this issue as close as possible to to that put forward by the United States, in the expectation Carter will bring Israel back to the bargaining table.

Robert C. Byrd, majority leader of the U.S. Senate, who is traveling through the Middle East, met Sadat and Khalil today.

Afterward, he read statement saying, "President Sadat, like President Carter, wants the negotiations to be resumed, and is ready to do so. He has demonstrated this time and again. I am confident President Sadat will spare no effort to work for a just and durable peace in the area."

That appeared to allign the United States and Egypt against the Israelis, who have said that the treaty text published last week is final and that they will not accept any timetable for elections in the occupied West Bank and the Gaza Strip. If there are to be more negotiations, as Carter and Secretary of State Cyrus Vance say there should be those are the matters Egypt wants to thrash out.

The latest version of Egypt's negotiating position, published in the Cairo press today, differs only marginally by Defense Minister Kamal Hassan Ali, head of Egypt's delegation at the Washington talks, and by Boutros Ghali, the acting foreign minister.

The Egyptian want an exchange of letters, including the treaty text but equally binding, that would provide for negotiations on establishment of Palestinian self-government in the occupied territories to begin within a month after the treaty is signed. Elections for local self-governing bodies there would come before the end of 1979.

Earlier, the Egyptians had been asking for elections within six months, at least in Gaza, but they alreadly had specified their willingness to accept the American formulation, setting the end of 1979 as a "basis of negotiations."

Egypt wants the timetable because under the Camp David agreements the five-year transition period leading to Palestinian self-rule would not begin until the autonomous local government is set up.

Cairo - anxious to show the other Arabs that it is not abandoning the Palestinians - is determined not to let the Israelis stretch that out by claiming it is impossible to hold elections.

The Israelis refuse to commit themselves to a timetable that Palestinian reluctance may make it impossible to meet, fearing that if the fixed sate goes by without elections, provisions of the Egyptian-Israeli treaty could be endangered.

The other issue is the wording of Article 6 of the draft treaty, specifying the Egypt's obligations under the accord would prevail over any other Egyptian treaty commitments. They Egyptians say they do not wish to make such a commitment so long as Israel remains technically at war with its other Arabs neighbors.

It is unclear how long it might take to resolve these issues. But it appears unlikely a treaty can be signed by Dec. 17, the end of the three-month period envisioned in the Camp David accords.