Israel says it will allow security forces loyal to Palestinian President Mahmoud Abbas to be supplied with weapons from third countries.
Israel says it will strictly control who receives the weapons
The announcement follows clashes between Mr Abbas's supporters and rivals from the Hamas militant group.
But Mr Abbas's office denied the story. A BBC correspondent said he might not want to be seen accepting Israeli help.
Earlier, Mr Abbas challenged Hamas to accept a joint political programme with his Fatah faction or face a referendum.
The plan, drawn up by jailed Palestinian leaders from all the main factions, says attacks on Israel should be limited to the land occupied by it since 1967 - implying recognition of Israel within its pre-1967 borders.
Mr Abbas gave Hamas a 10-day deadline to accept the proposal, which also calls for a national unity government.
The president was speaking at a conference aimed at ending violence and divisions between his own Fatah party and Hamas.
Mr Abbas said the time had come for Palestinians to act
Tensions between the two groups have spilled over into clashes in recent weeks, with at least 10 people killed this month.
Hamas has also deployed a new, independent security force in Gaza - seen as a direct challenge to the official security forces loyal to Mr Abbas.
Israel said it had decided to authorise deliveries of light weapons and ammunition to the presidential guard.
"At issue are several hundred weapons imported from foreign countries which will be transferred under tight control by us. We will know exactly to whom and where they are being delivered," a defence ministry official told the AFP news agency.
Mr Abbas's spokesman Nabil Abu Rudeina, however, said the "announcement made by the Israeli defence ministry is false".
The president's credibility could suffer if he were seen to be accepting Israeli help to defend himself from some of his own people, says the BBC's correspondent in Jerusalem, James Reynolds.
'Nation in danger'
Mr Abbas used the first day of talks with Hamas to make his shock ultimatum on political unity.
He called for a joint programme based on the 18-point plan announced two weeks ago by jailed leaders from across the Palestinian political spectrum.
"The situation is getting more dangerous. The whole nation is in danger. We can't wait for the rest of our lives," Mr Abbas said.
The plan, which would implicitly recognise the existence of Israel, received a mixed response from Hamas, which officially wants an Islamic state across Israel, the West Bank and Gaza.
Hamas' Abdel Aziz Dweik, speaker of the Palestinian Legislative Council, described the proposal as a good basis for dialogue, saying: "Returning to the people is one of the most important principles in democracy."
But Hamas' chief spokesman, Sami Abu Zuhri, said: "It represents an attempt to apply pressure with the aim of imposing a certain vision and conditions on the dialogue."