U.S. President Barack Obama said Monday no decision had been made on whether to send weapons to Ukraine to help Kiev battle pro-Russian separatists, as he warned the West would not allow Russia to redraw Europe's borders by force.

Obama, who has faced increasing calls from domestic critics to supply the outmatched Ukrainian army with more weapons to shore up its faltering defenses, said he was still mulling his options.

The United States is reportedly reconsidering a decision to invite Israel to a conference expected to be held in Washington next week after Lebanon decided to boycott it over claims that it cannot take part in a meeting to confront terrorism with the Jewish state's participation.

According to As Safir newspaper published on Monday, Lebanon's decision created a fuss among European countries that began wondering about the matter, which caused Washington to hesitate in its invitation.

Hatem is only 14 but has already lived through three wars with Israel. Now the young Gazan says he is making sure he'll be ready to fight in the next one.

"The Israelis killed my niece last summer. Now I want to kill them," he told Agence France Presse after completing a week-long youth training camp with militants from the Ezzedine al-Qassam Brigades, the armed wing of the Islamist Hamas movement.

Iraqi troops will begin a ground offensive "in the weeks ahead" to take back swathes of the country seized by the Islamic State (IS) group, the U.S. coordinator for the international coalition against the jihadists said Sunday.

"There will be a major counter offensive on the ground in Iraq," top U.S. envoy John Allen said in an interview with Jordan's official Petra news agency.

Syrian Kurdish forces have recaptured more than a third of the villages around Kobane from the Islamic State group since routing the jihadists from the town a fortnight ago, a monitor said Sunday.

"The (Kurdish) People's Protection Units (YPG) have recaptured 128 villages out of some 350 in the past two weeks," said Syrian Observatory for Human Rights director Rami Abdel Rahman.

An international coalition battling against Islamic militants in Iraq and Syria is beginning to win back territory and deprive the jihadists of key funds, U.S. top diplomat John Kerry said Sunday as he denounced the group's "new level of depravity".

Washington has rallied more than 60 countries in the fight against the Islamic State group, and while Kerry told a global security conference it would be a long battle, he said there were signs the strategy was working.

Iran's supreme leader Ayatollah Ali Khamenei said Sunday that he would rather see no deal reached with major powers on his country's nuclear programme than one that undercut national interests.

His comments came as U.S. Secretary of State John Kerry met Iranian counterpart Mohammad Javad Zarif for a second time on the sidelines of a security conference in Germany, to ratchet up efforts for a lasting nuclear accord.

The United States delivered on Sunday a shipment of military vehicles, weapons and ammunition to Lebanon as of Washington's pledge to aid the Lebanese military in its combat against terrorists.

The state-run National News Agency reported that the shipment was handed at Beirut's port in the presence of U.S. and Lebanese officials.

U.S. Secretary of State John Kerry ruled out extending a March 31 deadline for Iran nuclear talks unless the basic framework of an agreement is hammered out, speaking in an interview aired Sunday.

"The only chance I can see of an extension at this point in time would be that you really have the outlines of the agreement," Kerry said in the interview on NBC's "Meet the Press" taped Saturday in Munich.

Argentine-led forensic experts strongly criticized Mexico's investigation into the presumed massacre of 43 missing students on Saturday, insisting the probe must remain open as they listed a series of mishaps.

The Argentine Forensic Anthropology Team, with experts from 30 countries including the United States, Canada and France, issued a 16-page statement questioning the conclusions of the Mexican attorney general's office.