The Palestinian militant group Hamas has angrily condemned an Israeli operation which rounded up 150 people in the West Bank overnight, saying it had damaged prospects for a ceasefire.
Israel has vowed to wipe out Hamas
"We are facing a Zionist assault and it is not logical to ask us to accept a truce under these conditions," said Abdel-Aziz al-Rantissi, a Hamas leader.
The Israelis say the operation followed warnings of planned attacks against civilians.
Earlier reports had suggested Hamas was close to announcing a temporary ceasefire.
Palestinian Prime Minister Mahmoud Abbas - also known as Abu Mazen - has been trying to persuade Palestinian militants to stop attacking Israel, in line with the latest US-backed peace plan, called the roadmap.
The Israelis detained 130 people in the town of Hebron, and 20 in Nablus.
An army spokeswoman said those rounded up were being interrogated. Some have already been released.
"Hamas will evaluate its position [on the truce] when the time is appropriate, and it cannot do so as [Israel] raids Hebron," Mr Rantissi said.
"We cannot make up our minds with our neck under the sword," he said.
An Israeli adviser, Zalman Shoval, told the BBC that the operation would help the Palestinian Authority take over security arrangements.
But a Palestinian adviser, Michael Tarazi, said such action would only serve to undermine the Palestinian Authority.
"It is an Israeli madness aimed at undermining any move forward," Palestinian cabinet minister Yasser Abed Rabbo told the Reuters news agency.
"These arrests are an attempt to sabotage the understanding with Hamas."
Israel has rejected the proposal for a ceasefire with the militants.
"It's unacceptable for the Palestinian Authority, Israel and the United States to agree to a situation in which a certain Hamas leader decides when progress [on the roadmap] will be made," said Major General Amos Gilad.
There has so far been no reaction from Washington to the round-up.
But in a rare rebuke, US Secretary of State Colin Powell said on Sunday that the shooting of a Hamas commander on Saturday was a "matter of concern".
US National Security Adviser Condoleezza Rice is to arrive in the region at the weekend.