By Humeyra Pamuk, Jonathan Landay and Max Hunder

MUNICH, Feb 14 (Reuters) - Secretary of State Marco Rubio cast the United States as the "child of Europe" in a message of unity on Saturday, offering some reassurance as well as levelling more criticism at allies after a year of turmoil in transatlantic relations.

Rubio was addressing the annual Munich Security Conference, where Europe's leading powers have tried to project their own independence and strength while straining to keep an alliance with the U.S. under President Donald Trump alive.

LONDON/NAIROBI, Feb 14 (Reuters) - A feud between Saudi Arabia and the United Arab Emirates across the Horn of Africa is overshadowing this weekend’s African Union summit, though most of the continent’s leaders will try to avoid taking sides, nine diplomats and experts said.

What began as a rivalry in Yemen has spread across the Red Sea into a region riven with conflicts - from war in Somalia and Sudan to rivalry between Ethiopia and Eritrea and a divided Libya.

BEIRUT, Feb 14 (Reuters) - Former Lebanese Prime Minister Saad al-Hariri, one of the country's best-known politicians, indicated on Saturday that his party would contestupcoming elections, four years after he stepped back from public office.

In a speech marking the 21st anniversary of the assassination of his father Rafik, who was also prime minister, Saad told supporters in Beirut that others would “hear our voice, and count our votes” when elections take place.

By Humeyra Pamuk

MUNICH, Feb 14 (Reuters) - Iranian opposition figure Reza Pahlavi on Saturday said U.S. military intervention in Iran could save lives and urged President Donald Trump's administration not to spend too long negotiating with Tehran's clerical rulers on a nuclear deal.

The exiled son of Iran's toppled shah told Reuters in an interview that there were signs that the Iranian government was on the brink of collapse and that an attack could weaken it or accelerate its fall.

About 200,000 people joined a demonstration against the Iranian government in Munich on Saturday, police said, as world leaders gathered nearby for a security conference.

The pro-monarchist protesters rallied on the German city's Theresienwiese fairgrounds, denouncing the leadership of Iran's Islamic Republic following the deadly repression of nationwide protests in January.

Human rights groups have reported that thousands of protesters were killed in Iran.

The exiled son of Iran's last shah said he was ready to lead the country to a "secular democratic future" at a rally in Munich on Saturday, after US President Donald Trump said a change of power would be the "best thing".

It came as Washington continued to engage diplomatically with Tehran's government, with Switzerland on Saturday confirming that mediator Oman would host a fresh round of talks in Geneva next week.

MUNICH, Feb 14 (Reuters) - The European Union should "bring to life" a mutual defence pact anchored in its founding treaty, European Commission President Ursula von der Leyen said at the Munich Security Conference on Saturday.

"Mutual defence is not an optional task for the European Union. It is an obligation within our own treaty," von der Leyen said in a speech at the conference.

"It is our collective commitment to stand by each other in case of aggression, or in simple terms: one for all and all for one. And this is Europe's meaning."

Feb 14 (Reuters) - Medecins Sans Frontieres has halted "non-critical" medical activities at a major hospital in southern Gaza following reports from patients and its own staff of armed men inside the facility and concerns over the movement of weapons within it.

MSF's statement appeared to mark the first time that an international humanitarian group in Gaza has publicly reported the presence of armed men in a hospital or the possible use of such a facility for moving weapons.

Palestinian president Mahmud Abbas called on Saturday for the removal of "all obstacles" he said Israel has imposed on implementing phase two of the Gaza ceasefire.

"We emphasise the need to lift all obstacles imposed by the Israeli occupation on the implementation of the provisions related to the second phase of the agreement," Abbas said, in a speech read by his prime minister Mohammed Mustafa at an African Union summit in Ethiopia.

This included the work of a technocratic committee established to oversee the daily governance of Gaza, he added.

PALM BEACH, Florida, Feb 13 (Reuters) - Two sets of diplomatic negotiations, on Ukraine and Iran, are set to take place in Geneva on Tuesday, a source briefed on the matter told Reuters on Friday.

A U.S. delegation including envoys Steve Witkoff and Jared Kushner will meet with the Iranians on Tuesday morning, the source said. Representatives from Oman will be on hand and mediate the U.S.-Iran contacts, the source said.

Witkoff and Kushner will then participate in trilateral talks with representatives from Russia and Ukraine in the afternoon, the source said.