Israeli armor and infantry went into Ramallah Monday morning, once again barricading Yasser Arafat inside the Palestinian Authority compound while sweeps for suspected militants were conducted in the city outside. 

Twenty Palestinians were rounded up in the dawn operation, hours before Israeli Prime Minister Ariel Sharon was to meet President Bush at the White House. 

In Gaza City, Palestinian police arrested Sheik Abdullah Shami, the local Islamic Jihad leader, on orders issued by Arafat after the group killed 17 Israelis in a bus bombing Wednesday. 

The PA compound in Ramallah, battered by Israeli fire several times over the past six months, most recently on Thursday, was left alone by the military this time. Palestinian officials said Arafat was inside but unharmed. 

Gunfire in the streets of Ramallah killed one Palestinian, the Israeli army said, while two Palestinians and two soldiers were wounded. 

The incursion began around 4 a.m. Monday when tanks, armored personnel carriers, jeeps and infantry on foot entered Ramallah, which is just a few miles north of Jerusalem. 

Soldiers moved among houses around the Amari refugee camp, entering one house as two trucks parked outside. Troops were on the move throughout the city and in suburban areas. 

The Israeli army statement said the troops would remain in Ramallah for a "limited time." Also, soldiers detained several suspects in nighttime raids in other parts of the West Bank, the statement added. 

In a followup to a massive military incursion in the West Bank that ended a month ago, Israeli troops have been staging almost daily in-and-out raids in Palestinian cities, towns and villages. 

In most instances, the troops have gone in for only a few hours to arrest suspects based on intelligence information. But in some cases they have stayed for days, conducting mass roundups of hundreds of Palestinian men and imposing round-the-clock curfews. 

The Ramallah incursion came a day after Arafat named a new, smaller Cabinet that includes a new minister to oversee the security forces. The move follows strong calls for reform by ordinary Palestinians and Western governments. 

Also, the Palestinians will hold municipal elections in the fall, followed by presidential and parliamentary elections in January. 

Arafat's slimmed down Cabinet has been reduced from 31 to 21 ministers. In the most important change, Arafat named Abdel Razak Yehiyeh, 73, as interior minister — a position that puts him in overall charge of the security forces. 

Arafat had kept the post for himself for the past eight years, but came under intense pressure from the United States and Israel to revamp the security forces to prevent attacks against Israel. 

Israeli Defense Minister Binyamin Ben-Eliezer reacted skeptically to the naming of Yehiyeh, saying it signified Arafat was not serious about reform. 

"This man represents the very old generation. So once again we have a commitment to the past and not to the future," Ben-Eliezer said. 

Yehiyeh, a former guerrilla commander, has not held any high-profile positions recently, and his selection bypasses more prominent figures. 

Dogged by accusations of widespread corruption in his government, Arafat named a new finance minister, Salem Fayad. He has worked in Jerusalem for the International Monetary Fund in recent years, and has called for greater financial accountability in the Palestinian government. 

Many Palestinians cite new elections as the most important reform. Since the Palestinian Authority was formed in 1994, elections have been held only once, in 1996. 

Meanwhile, in the Gaza Strip, powerful explosion rocked the Jebaliya refugee camp early Monday, destroying one building and damaging nearby homes, witnesses said. 

An 18-year-old woman was killed and at least 25 people were injured, including three in critical condition, hospital officials said. Witnesses said the blast came from inside the building, but Palestinian officials would not comment on the cause. 

Meanwhile, the Bush-Sharon meeting will be their sixth in a little over a year. In an opinion article in the New York Times, Sharon wrote that Israel was prepared to resume negotiations if Palestinian attacks stop, though he doesn't believe a final settlement could be reached now. 

"The only serious option ... is one based on a long-term interim agreement that sets aside for the future issues that cannot be bridged at present," Sharon wrote. The Palestinians reject the idea of an interim accord. 

Sharon, citing Israel's security concerns, said Israel would not pull out of all the West Bank and Gaza Strip, which it captured in the 1967 Mideast War, or redivide Jerusalem. "Israel will not return to the vulnerable 1967 armistice lines," he wrote. 

The Palestinians want the West Bank and Gaza for their future state, with a capital in east Jerusalem. 

The Associated Press contributed to this report.