Libya's foreign minister has not been offered immunity after his surprise arrival in Britain, London said Thursday, while urging other members of Moammar Gadhafi's "crumbling" regime to quit.

Moussa Koussa, a former head of Libyan intelligence and one-time ambassador to Britain, arrived "under his own free will" at Farnborough airport southwest of London on Wednesday, British Foreign Secretary William Hague said.

NATO chief Anders Fogh Rasmussen said Thursday he opposed arming Libyan rebels, stressing NATO had intervened to protect and not to arm Libyans.

"We are there to protect the Libyan people, not to arm the Libyan people," Rasmussen told reporters.

Kuwait is to expel a number of Iranian diplomats for alleged links to a spy ring working for Tehran, reportedly since the 2003 invasion of Iraq, the foreign minister announced on Thursday.

"There will be action against a group of Iranian diplomats ... They will be considered persona non grata and expelled from Kuwait," Sheikh Mohammed al-Sabah told reporters.

President Ali Abdullah Saleh and his opponents have set the scene for another tense Friday in a two-month-long showdown with calls for rival demonstrations in the Yemeni capital.

State news agency Saba said tribal chiefs, clerics, civil society figures, youths and supporters from the countryside were streaming into Sanaa on Thursday in response to the longtime president's call for a show of solidarity.

Protesters called for rallies across Syria after weekly Muslim prayers on Friday, upping the pressure on President Bashar Assad after he dashed hopes of an end to decades of emergency rule.

"Our date is Friday, from all houses, all places of worship, every citizen and every free man, to all squares, for a free Syria," said a statement posted Thursday on Facebook group The Syria Revolution 2011.

U.S. President Barack Obama should abandon his policy of engaging Syria and stand foursquare behind opposition to the government of President Bashar al-Assad, lawmakers urged Wednesday.

Republican Senator John McCain and Independent Senator Joe Lieberman said Obama's effort to engage rather than shun Damascus had "little to show for it" and declared it was time to back protesters against Assad's rule.

Libyan leader Moammar Gadhafi suffered a major blow Wednesday with the defection of his foreign minister even as his forces again proved too strong for the rebels' rag-tag army.

Gadhafi's forces overran the towns of Ras Lanuf, Uqayla and Brega, rebels reported, scattering the outgunned insurgents as world powers mulled arming the fighters to help them oust the Libyan strongman.

A key speech by Syrian President Bashar al-Assad on Wednesday lacked real substance and failed to mention the kind of reforms his people are demanding, the United States said.

In a bid to quell weeks of protests against his iron-clad rule, Assad earlier gave a rare address in parliament.

U.S. President Barack Obama said he is confident that Moammar Gadhafi will "ultimately" step down, as a new poll Wednesday found nearly half of Americans were opposed to U.S. military involvement in Libya.

Obama warned Tuesday he had not ruled out supplying arms to rebels seeking to oust him, and said the "noose is tightening" around the Libyan strongman.

Bahrain's Shiite opposition head Ali Salman on Wednesday warned Iran and Saudi Arabia against using his country as a "battlefield" in a proxy war.

Salman urged Iran to keep out of the Sunni-ruled state's affairs and called on Saudi troops to leave the country.