SHARM EL SHEIKH, Egypt — Three Persian Gulf monarchies on Friday pledged a total of $12 billion in aid to Egypt, adding to a total of more than $20 billion already contributed since the military ouster of President Mohamed Morsi of the Muslim Brotherhood nearly 20 months ago.

The pledges came on the first day of an international investment conference here that the leader of Egypt’s military-backed government, President Abdel Fattah el-Sisi, has made a centerpiece of his economic program. The large sums underscored his government’s continued dependence on the backing of the oil-rich gulf monarchs.

Officials representing the monarchies — Saudi Arabia, the United Arab Emirates and Kuwait — each pledged $4 billion on Friday. The United Arab Emirates said it would provide $2 billion in deposits to Egypt’s central bank reserves and another $2 billion in other economic assistance. Saudi Arabia and Kuwait were less specific.

The pledged contributions will bolster Egypt’s balance sheet at a moment when the government has come under renewed pressure. Its international financial reserves fell to $15.5 billion in February, down from $17.3 billion a year earlier and $36 billion before the uprising in 2011, declines that have threatened to undermine the value of its currency.