* Hamas warned to prevent Palestinian rocket fire
* Delegations from 18 countries honouring ex-premier
* Biden, Netanyahu to discuss Iran, Palestine talks (Adds details on U.S. delegation)
JERUSALEM, Jan 13 (Reuters) - Israel beefed up security for former Prime Minister Ariel Sharon's funeral near the Gaza border on Monday and warned the enclave's Palestinian rulers not to allow rocket fire during the ceremony, which U.S. Vice President Joe Biden will attend.
Sharon died at the age of 85 on Saturday after eight years in a coma caused by a stroke. A memorial service will be held on Monday in parliament in Jerusalem and an afternoon funeral near the Sharon family farm some 10 km (6 miles) from Gaza.
The United States was among 18 countries to send delegations to the state ceremony for Sharon in Jerusalem. The White House said Biden would also travel to the burial at Sycamore Farm's Poppy Hill, in the southern Negev desert.
An Israeli security source said Israel had "passed the message" to Gazan authorities to prevent any rocket fire during the funeral. Gaza is governed by Hamas Islamists who fought several times with Israel over the past few years.
"It was made clear to them that tomorrow would be a very bad day for anyone there to test Israel's patience," said the source, who spoke on condition of anonymity.
There was no immediate response from the Hamas government or other armed Palestinian factions. Egyptian officials, who in the past have served as mediators between Israel and Gaza, were unavailable for comment.
A Reuters correspondent heard two explosions in northern Gaza on Monday morning which sounded like rocket impacts. An Israeli military spokeswoman said there had been no launches across the border. Israeli media said the blasts appeared to have resulted from Palestinian militants testing their weapons.
At times of heightened tension Israel steps up aerial patrols of Gaza with combat helicopters and drones designed to spot Palestinian rocket crews and hit them with guided missiles before they can carry out launches.
Security sources said Israel had deployed an Iron Dome rocket interceptor near Sycamore Farm, which has been hit by Gaza-launched rockets in the past.
The rockets are often inaccurate and carry small warheads, causing relatively little damage. When fired in salvoes they spread panic and paralyse routine life in south Israel.
BIDEN, NETANYAHU TO TALK STRATEGY
How to handle Gaza is among the sticking points in Israel's U.S.-sponsored peace negotiations with Palestinian President Mahmoud Abbas, Hamas's rival based in the occupied West Bank.
During his brief visit to Israel, Biden will discuss the so far fruitless diplomatic efforts with Prime Minister Benjamin Netanyahu and President Shimon Peres, U.S. officials said.
The vice president will also seek to ease Netanyahu's concerns about world powers' interim nuclear deal with Israel's arch-foe Iran, which takes effect on Jan. 20.
Biden is seen by Israel and its U.S. supporters as one of its best friends in Washington in a career dating back to his decades on Capitol Hill, where he chaired the Senate Foreign Relations Committee before assuming the vice presidency.
He led a U.S. delegation to the funeral that included Congress members Eliot Engel of New York and Debbie Wasserman Schultz of Florida. He was also accompanied by U.S. Ambassador to Israel Dan Shapiro and former ambassador Daniel Kurtzer.
U.S. President Barack Obama, who took office in 2009 and made his first presidential visit to Israel last year, did not come. The only trip of his presidency to pay his respects to a foreign leader was last month, when he and First Lady Michelle Obama went to South Africa to attend a memorial service for former president Nelson Mandela, the anti-apartheid icon he hailed as an inspiration for his own career in public service.
Biden, who has held talks with more than half a dozen Israeli prime ministers over the years, last met Sharon in 2005.
Israel's Army Radio said there had been no intelligence indications that Palestinians were planning to shell Sharon's funeral. Yet authorities braced for any surprise.
"We are taking the full range of possible scenarios into account," southern police commander Yoram Halevy told the station. "The IDF (Israel Defence Forces) is prepared, informed and ready to respond if so required."
Since a 2012 eight-day war with Israel, which killed some 170 Palestinians and six Israelis, Hamas has largely held fire but smaller militant groups have occasionally challenged its authority with their own rocket attacks into the Jewish state. (Writing by Dan Williams; Additional reporting by Nidal al-Mughrabi; Editing by Jeffrey Heller, Meredith Mazzilli and Eric Walsh)