The US is concerned about the progress of democratic reform in Egypt, US Secretary of State Condoleezza Rice has said after talks with Egypt's leaders.
Discussions were "mutually respectful", Ms Rice stressed
Ms Rice said she told President Hosni Mubarak of her concerns about planned constitutional changes, due to be voted on in a referendum on Monday.
Opposition groups say the amendments, which include a ban on parties based on religion, will limit freedoms.
Mr Mubarak says reform is vital to tackle terrorism and sectarian tension.
Ms Rice visited Egypt as part of her attempts to press pro-American Arab states to do more to restart the stalled Middle East peace process.
Hopes and concerns
But her talks came amid domestic anger at the planned changes to Egypt's constitution, as well as apparent irritation from the Egyptian authorities at what they see as outside interference in their affairs.
On her way to Egypt, Ms Rice expressed concern at the planned changes, saying there was a danger that the process would not give a voice to all Egyptians.
Correspondents say she appeared to tone down her comments on Sunday when she addressed a joint news conference in Aswan with Egyptian Foreign Minister Ahmed Abul Gheit.
"I've made my concerns known, as well as my hopes, for continued reform here in Egypt," she said.
"The process of reform is difficult - it's going to have its ups and downs," said Ms Rice, adding that the issue was discussed in a "mutually respectful" way.
Mr Abul Gheit said the proposed changes were needed in a country that faced terror threats from "a number of hardliner and extremist types".
Ahead of his talks with Ms Rice, President Mubarak had robustly defended Egypt's position, saying his government would not bend to outside "pressure, dictation or prerequisites".
As well as banning the creation of political parties based on religion, the proposed amendments allow for the adoption of a new election law.
They would permit the president to dissolve parliament unilaterally and do away with the need for judicial supervision of every ballot box.
There have been calls for a boycott of Monday's referendum
If approved, the changes will also allow a new anti-terrorism law to be drafted to replace the emergency legislation that has been in place since 1981, when Mr Mubarak first became president following the assassination of Anwar Sadat.
The government says the changes will boost democratic practice in the county.
But the opposition, which includes the illegal but popular Muslim Brotherhood, say the changes will turn Egypt into a police state and are boycotting the referendum.