WASHINGTON (AP) _ President Bush was upbeat Thursday about Mideast peace prospects, attributing his optimism to the appointment of a new Palestinian prime minister.

``Of course we are going to make progress, yes we will make progress, absolutely,'' Bush told reporters before lunching at the White House with Sheik Hamad bin Khalifa al Thani, the emir of Qatar and an ally in the U.S. war with Iraq.

``The reason we will make progress is because the Palestinian Authority has now got a leader in the prime minister who has renounced violence,'' Bush said.

Also, the president said, the new Palestinian leader, Mahmoud Abbas, ``said he wants to work with us to make the area more secure. He understands what we know: That a peace process will proceed if and when there is a concerted effort to fight violence.''

Secretary of State Colin Powell will test that proposition this weekend. He flies to Israel Friday night for talks with Prime Minister Ariel Sharon in Jerusalem and Abbas in Ramallah on the West Bank.

Powell will leave a deputy, David Satterfield, behind for follow-up talks, and Edward Djerejian, a former U.S. ambassador and former assistant secretary of state, will be available for consultations, according to U.S. sources.

In northern Gaza, meanwhile, Israeli forces killed a senior Hamas militant in a missile strike.

Israeli helicopters fired three missiles at a car driven by Iyad al-Beack, 30, killing him and slightly wounding three bystanders. Two missiles hit Al-Beack's car and the third landed in the street.

Hamas officials identified Al-Beack, 30, as a former assistant to the commander of the Hamas military wing, Salah Shehadeh. Al-Beack was responsible for hiding militants, Hamas officials said.

The Israeli army, which confirmed the strike, said al-Beack was responsible for 16 attacks in which 19 Israelis were killed.

In Washington, the State Department spokesman, Richard Boucher, reiterated U.S. opposition to targeted killings. ``They undermine the efforts to achieve peace, they aggravate the situation in the region, and they do not contribute to progress on Palestinian civil and security reform,'' he said.

At the same time, Boucher said, ``There can be no excuse for the violence and terrorism that has been directed at the Israeli people.''

Bush said he was asking the Qatari emir how to ``work with the Arab world to encourage the Arab world to assume its responsibilities of stopping the funding of terror and working with the Palestinian Authority to encourage the habits of democracy and freedom.''

``So I am very optimistic,'' Bush said.

Powell plans to prod Sharon and Abbas to open negotiations for a peace accord aimed at establishing a Palestinian state by 2005.

In effect, Powell's assignment is to gain unqualified acceptance of a road map or blueprint for peacemaking producing by the Bush administration jointly with the United Nations, the European Union and Russia.

Key provisions include a ceasefire to end 31 months of violence, commitments by both Israel and the Palestinians to stop fighting, and a freeze on construction of homes for Jews on the West Bank as well as a rollback of some existing settlements.

Bush has tried to marginalize Yasser Arafat, the Palestinian leader, who authorized the appointment of his longtime lieutenant, Abbas, also known as Abu Mazen, as prime minister.

Whether Arafat will continue to play a leading role in dealing with Israel and on the issue of violence was not clear. Bush made no reference to Arafat or to his position as head of the Palestinian Authority.

Powell also is to hold talks in Egypt, Jordan and Saudi Arabia, then go to Bulgaria, Germany and Russia. In Russia, Powell will work on preparations for President Bush's meeting with Russian President Vladimir Putin at St. Petersburg to coincide with the former Russian imperial capital's 300th anniversary June 1.

Boucher, meanwhile, said Israel and the Palestinians had obligations and responsibility ``to take practical steps, concrete steps to further the process, to begin moving along the road of the road map.''

``It's time to focus on the practical steps they can take,'' he said.

Boucher said that the Palestinians need to focus particularly on the issue of security and that Israel and other governments ``need to see what they can do to support the transformation that is taking place in the Palestinian Authority.''