Top Trump adviser arrives for talks in Israel

US President Donald Trump's national security adviser arrived in Israel on Sunday for talks with Prime Minister Benjamin Netanyahu at a time of shared concerns over Syria, Iran and the Gaza Strip.

John Bolton said on Twitter he was "looking forward to meeting with PM Netanyahu and other officials beginning today to discuss bilateral concerns and a range of national security issues".

He also said in an interview with ABC News in the United States that he planned to discuss Iran's presence in Syria with Netanyahu when they meet on Monday morning.

"Certainly the objective of the United States, of Israel -- President Putin said it was Russia's objective -- is to get Iran, Iranian forces, Iranian militias, Iranian surrogates out of the offensive operations they're in both Syria and Iraq and frankly, to end Iran's support for (Lebanon's) Hezbollah," Bolton said.

He argued that Trump's withdrawal from the Iran nuclear deal and his reimposing of sanctions had "put a real crimp into the Iranian economy" and affected Tehran's ability to "conduct offensive operations" in the region. Bolton's trip will also take him to Ukraine and Geneva, where he will meet with his Russian counterpart Nikolai Patrushev on Thursday.

The meeting in Geneva is a follow-up to Trump's highly controversial July summit with Russian President Vladimir Putin in Helsinki, according to the White House.

Iran is backing Syrian President Bashar al-Assad in his country's civil war along with Russia and Lebanese Shiite group Hezbollah.

Netanyahu has pledged to prevent Iran, his country's main enemy, from entrenching itself militarily in neighbouring Syria, and a series of recent strikes that have killed Iranians there have been attributed to Israel.

Israel has also lauded Trump's withdrawal from the nuclear deal between Iran and world powers.

Netanyahu has held a series of recent talks with Putin on Iran's presence in Syria, pressing Moscow to guarantee that Iranian forces and their allies, such as Hezbollah, will be kept far away from the Israeli-occupied Golan Heights. Bolton's visit comes as speculation increases over efforts by Egypt and UN officials to secure a long-term truce between Israel and Hamas, the Palestinian Islamist movement that runs the Gaza Strip.

Months of tension along the Gaza border have led to fears of a fourth war between Israel and Hamas since 2008.

On Sunday, Israel closed its only crossing for people with the Gaza Strip following border clashes at the weekend, the latest tightening of its blockade of the Palestinian enclave.

Despite the closure, the past week has been notably calmer along the Gaza border.