An Israeli security official confirmed the visit, which was reported in Haaretz newspaper, but could not provide further details.

As well as discussing Tehran's nuclear programme, the major general also held talks with senior White House and intelligence officials in New York and Washington on "the Syria crisis and Hezbollah's increasing power in Lebanon," the paper said.

Citing a senior Israeli official, Haaretz said Iran was the main topic, with talks focused on next week's talks between Tehran and the P5+1 powers -- the United States, Russia, China, Britain, France and Germany.

Israel and most of the West believe Iran's nuclear energy programme masks a drive to develop atomic weapons but the two allies disagree on how imminent the threat is. Tehran denies such intentions.

US officials have warned against any pre-emptive military strike, with analysts predicting Iran could hit back at US and Israeli targets, with its Lebanese Shiite ally Hezbollah expected to launch rocket attacks on Israel.

According to the paper, Kochavi warned over Hezbollah's "increasing strength" and said internal tensions in Lebanon, combined with the instability in Syria, "increases the risk of escalation."

In recent weeks, Israel has spared no effort to ensure its concerns are well understood ahead of the May 23 P5+1 talks in Baghdad.

Earlier this month, National Security Adviser Yaakov Amidror toured European capitals meeting officials directly engaged in the Iran talks.

And last week, EU foreign policy chief Catherine Ashton made a surprise visit to Jerusalem to discuss the talks with top Israeli officials.

On Tuesday, Defence Minister Ehud Barak flew to Washington for the third time in recent months for talks with his American counterpart, which were also expected to deal with Iran.

Before leaving, Barak complained that the world's demands of Iran were "minimalist" and would not succeed in making it halt its nuclear drive.

"This is one of the options," said the official who wished to remain anonymous.

"Right now there is no such situation requiring Turkey to invoke Article 5, but we will consider this option in the event of a serious attack on our sovereignty."

He was referring to the clause which stipulates that an attack against a member of the North Atlantic Treaty Organisation is considered an attack against all members of the alliance.

Syrian gunfire targeting refugees trying to cross into Turkey hit a camp on the Turkish side of the border last month, leaving two Syrians dead, according to eyewitnesses.

After the incident, Ankara has said it might call in NATO to help protect its border, amid heightened tensions with Damascus over the deadly conflict in Syria, which has seen thousands of people crossing into Turkey.

When asked on April 12 what Turkey's response would be to conflict spilling over the Syrian-Turkish border, Prime Minister Recep Tayyip Erdogan said that "we have several options."

"First of all, there is an option of invoking Article 5 of the NATO treaty," he said.

The Turkish official said there had been no serious attack thus far emanating from Syria against Turkey but "if it happens, we have the right to invoke Article 5 like each member state of the alliance. This is our natural right."

NATO invoked Article 5 of the Washington Treaty for the first time in its history following the 9/11 attacks against the United States.

The Syrian crisis is expected to appear on the agenda of NATO summit in Chicago on May 20-21, the official added.