MANAMA: Representatives of the oil-rich states making up the Gulf Cooperation Council were gathering in Manama on Monday to discuss economic integration and security in the face of growing regional tensions.

The summit starting later Monday would focus on strengthening "Gulf unity... especially politically, economically, in defence, security and culturally," news agency BNA quoted Bahrain's Foreign Minister Sheikh Khaled bin Ahmed Al-Khalifa as saying.

He made the speech during a foreign ministers' meeting held behind closed doors late on Sunday, ahead of the summit.

The two-day Manama meeting will also discuss other regional issues including the conflict roiling Syria and the situation in Yemen, sources said.

However, four of the six heads of state will not attend the annual gathering.

King Abdullah of Saudi Arabia is convalescing after a back operation in November, while Qatar is sending its crown prince, the United Arab Emirates its vice president, and Oman its deputy prime minister.

Kuwait will be represented by its emir, Sheikh Sabah al-Ahmed Al-Sabah.

The GCC states -- Bahrain, Kuwait, Oman, Qatar, the UAE and Saudi Arabia -- have a combined population of around 46 million, the majority of whom are foreigners.

Their overall GDP in 2011 amounted to 1.371 trillion dollars, a diplomatic source said.

In 2003, they launched a symbolic customs union which has been beset with problems, failing to meet its target date of 2005, with the transition period systematically extended to 2015.

And a monetary union announced in 2009 with the aim of creating a common currency has also failed to materialise, with just four nations -- Bahrain, Kuwait, Qatar and Saudi Arabia -- signing up to it.

The six monarchies will also discuss plans to expand a security treaty they signed in 1994 with the aim of increasing security cooperation in the face of Arab Spring uprisings, sources said.

Bahrain is still trying to cope with a Shiite-led uprising it crushed last year with the backing of Gulf troops, while Kuwait is rocked by a political crisis which has seen the opposition staging protests against an amendment to the electoral law.

In the normally sleepy Oman, demonstrators took to the streets last year to demand improved living conditions and reforms, in a move that quickly subsided.

Saudi Arabia's Shiite-populated oil-rich Eastern Province, meanwhile, has been the site of sporadic protests, while the United Arab Emirates recently arrested some 60 Islamist dissidents it claims were plotting against state security.

The summit will also discuss relations with Shiite Iran -- eyed with mistrust by most Gulf states, notably key regional power Saudi Arabia.

Iran is "interfering to provoke sedition, and this is unacceptable," pan-Arab Al-Hayat daily on Monday quoted Saudi Foreign Minister Prince Saud al-Faisal as saying in Manama.