CAIRO, Sept 13 (Reuters) - Islamic State militants in Iraq and Syria are forging ties with other extremist groups in the region, Egypt's foreign minister said on Saturday, backing Washington's call for global action to counter the threat.

Militant groups that share Islamic State's ideology and "take Islam as a cover" must be dealt with, Foreign Minister Sameh Shukri told a joint news conference with U.S. Secretary of State John Kerry in the Egyptian capital.

Egypt's strong public support for the U.S. campaign against Islamic State contrasts with a mixed response elsewhere in the region and demonstrates how far Cairo has come in restoring its place as a premier U.S. partner in the Arab world since its authoritarian crackdown and military takeover last year.

"We will take all measures that are intended to eliminate this phenomenon altogether, whether in Libya or any other part of the Arab world or in the African continent in particular," Shukri said.

Egypt's call for international action gives a needed boost to Kerry's bid to build global support for President Barack Obama's plan to strike both sides of the Syrian-Iraqi frontier and defeat Islamic State Sunni fighters.

Kerry won backing on Thursday for a "coordinated military campaign" against Islamic State from 10 Arab countries - Egypt, Iraq, Jordan, Lebanon and six Gulf states including rich rivals Saudi Arabia and Qatar.

But the specific role of many countries in the coalition remains unclear. Few have publicly committed to military action or other steps, particularly in Syria where a three-year civil war still rages. Europe's response has been mixed.

Egypt's role is potentially crucial. Egyptian security officials fear they face a threat from Egyptian militants based across the border in Libya and from the Sinai-based Ansar Bayt al-Maqdis, Egypt's most dangerous militant group. Both are linked to or inspired by Islamic State.

Islamic State, fighting to redraw the map of the Middle East, has been coaching Ansar, which has killed hundreds of members of the Egyptian security forces over the last year, a senior Ansar commander told Reuters this month.

"Ultimately this extremist ideology is shared by all terrorist groups. We detect ties of cooperation between them and see a danger as it crosses borders," said Shukri.

"INTELLECTUAL AND CULTURAL CAPITAL"

At the news conference, Kerry suggested Egypt, regarded as intellectual hub in the Arab world, can exert enormous influence in countering Islamic State's ideology from its sheer size as the Arab world's most populous state to its powerful clerics.

The United States wants Egypt to use its leading Islamic authority Al-Azhar, a thousand-year-old seat of religious learning, to send a message of moderation across the Middle East to counter Islamic State's extremist ideology.

"As an intellectual and cultural capital of the Muslim world, Egypt has a critical role to play in publicly renouncing the ideology ISIL disseminates," said Kerry, referring to the group by its former name Islamic State in Iraq and the Levant.

Kerry's message in Cairo comes two days after he urged Gulf Arab foreign ministers to suppress all financing of Islamic State, including private money in countries such as Qatar and Kuwait where U.S. officials say enforcement has been weak.

The United States called on each country to work with clerics to convey a message that Islamic State's ideas are contrary to Islam, and to use their influence on regional television stations to broadcast anti-extremist programming.

Obama's plan to fight Islamic State simultaneously in Iraq and Syria thrusts the United States directly into the midst of two different wars, in which nearly every country in the region has a stake against the backdrop of Islam's 1,300-year-old rift between Sunnis and Shi'ites.

Islamic State is made up of Sunni militants, who are fighting a Shi'ite-led government in Iraq and a government in Syria led by members of a Shi'ite offshoot sect.

In Syria, Turkey has backed mainly Sunni rebels fighting against President Bashar al-Assad. Although it is alarmed by Islamic State's rise, Turkey is wary about any military action that might weaken Assad's foes, and is concerned about strengthening Kurds in Iraq and Syria.

Lebanese Foreign Minister Gebran Bassil told Reuters some Arab states at talks in Jeddah on Thursday had proposed expanding the campaign to fight other Islamist groups besides Islamic State, a move Turkey would also probably oppose.

Egypt would welcome any move that would further isolate the Muslim Brotherhood, the Islamist group that the army removed from power last year.

Egyptian authorities have cracked down on the Brotherhood, killing hundreds of members and jailing thousands of others. Egypt has declared the Brotherhood a terrorist group.

Qatar has asked seven senior figures from Egypt's outlawed Muslim Brotherhood to leave the country, the movement said on Saturday, following months of pressure on the Gulf Arab state from its neighbours to stop backing the Islamists.

After Cairo, Kerry flies to Paris where he will attend a conference on Monday that will bring Iraqi authorities together with 15 to 20 international players. The talks come ahead of a U.N. Security Council ministerial meeting on Sept. 19 and a heads of state meeting at the U.N. General Assembly later this month.

France has sent weapons to Kurdish fighters in Iraq and humanitarian aid. But what it can offer the U.S.-led anti-Islamic State campaign is limited, with its forces already stretched.

Britain, Washington's main ally in 2003, has sent mixed messages. It has stressed the West should not go over the heads of regional powers or neglect the importance of forming an inclusive government in Iraq. Like France, it is also cautious about action in Syria because of legal questions and Syrian government air defenses.

Most other European countries appear unwilling to go beyond humanitarian and logistical aid. (Writing by Michael Georgy and Jason Szep; Additional reporting by John Irish in Paris; Editing by Dominic Evans and Lisa Shumaker)