The Prime Minister has criticised Russia over its relationship with Syria, after a visit to Saudi Arabia to "strengthen co-operation" with the desert kingdom.
In an interview with Saudi television network Al-Arabiya, David Cameron said:
"I would urge the Russians and the Russian Government, even at this late stage, to look very carefully at why it keeps doing what it's looking to do on Syria.
"This is appalling bloodshed, appalling murder on the streets of Syria. The whole Arab League has come together and said it's unacceptable and others need to listen to that and act on that at the UN. Britain stands ready to do that".
Speaking on Britain's policy towards Syria, Cameon added:
"We stand ready as a permanent member of the UN Security Council to take a fresh resolution to that council, based on what the Arab League is doing and saying, and daring others that if they want to veto that resolution to try to explain why they are willing to stand by and watch such appalling bloodshed by someone who has turned into such an appalling dictator".
The comments were made during talks in Riyadh with King Abdullah, designed to deepen ties with the oil-rich nation, despite criticism of British arms sales to the desert kingdom and concerns about the country's human rights record.
The trade between Britain and Saudi Arabia is worth £16bn a year and the kingdom is Britain's biggest trading partner in the Middle East.
"They discussed the importance of the UK-Saudi bilateral relationship and agreed to strengthen co-operation in a range of areas," Downing Street said in a statement.
The government sees strong relations with the Saudis as vital to advancing Britain's interests in the region on a range of issues including energy security, counter-terrorism and political reform.
Saudi Arabia is Britain's biggest trading partner in the Middle East with bilateral trade worth £15 billion a year and Saudi investment in the UK worth more than £62 billion.
It is reported that negotiations are under way on the Saudi purchase of 48 Typhoon Eurofighter aircraft.
But Cameron's first visit to the nation since becoming premier came as the Committees on Arms Export Controls published details of questions raised with the Government over the licensing for a range of equipment.
Export permission was granted for bomb equipment, components for military combat vehicles and helicopters, weapon sights and communications technology.
MPs questioned why, given the unrest in Saudi Arabia early last year, licences had not been revoked as part of the Government's review of arms sales to the Middle East and North Africa.
As the Prime Minister met King Abdullah, reports emerged of clashes between protesters and security forces in the east of the kingdom which left one man dead.
Troops fired on demonstrators throwing rocks last night in the oil-rich Qatif province, according to Shiites.
The Interior Ministry said security forces returned fire after coming under attack when fleeing their patrol vehicle after it was hit by a firebomb.
Liberal Democrat MP Martin Horwood, co-chair of his party's Parliamentary Party Committee on International Affairs, said: "Liberal Democrats are very worried about the Saudi kingdom's terrible record on human rights including those of women, religious minorities, foreign workers and political opponents of the regime.
"The coalition Government did the right thing to champion Arab democracy throughout the Arab Spring and we must not send out mixed messages now."
Amnesty International also called on Mr Cameron to be "completely frank and firm" with King Abdullah about Saudi's "shocking disrespect for basic human rights".
"In Saudi Arabia women are treated as second-class citizens," UK campaigns director Tim Hancock said.
"They can be flogged if they're caught driving a car and they have to receive the permission of a male guardian before they can travel, start a job or get married.
"If Samantha Cameron were on this visit she would be unable to drive or move around freely without risk of arrest."
Asked whether the Prime Minister had raised criticism of Saudi's human rights record, a Downing Street spokeswoman said: "We have a full and wide ranging discussion with Saudi on these issues."
She stressed that Saudi had "made some progress" on human rights recently, such as women standing for elections. Mr Cameron and King Abdullah discussed the Arab Spring and what that meant for "reform across the region".
Mr Cameron also spoke to King Abdullah about problems with piracy and lawlessness in Somalia.
The visit came amid rising tensions between the West and Iran, Saudi's arch-rival in the Gulf.
Mr Cameron warned Iran that the world would "come together" to prevent it closing the Strait of Hormuz oil shipment route, which Tehran has threatened to do if it is attacked or heavy sanctions are imposed.
Western governments, including Britain, have moved to step up sanctions over Iran's controversial nuclear programme, threatening an embargo on vital oil exports that has drawn an angry response from Tehran.
In an interview with Saudi television channel Al Arabiya, Mr Cameron said today: "In terms of the Straits of Hormuz, it is in the interests of the whole world that those straits are open and I'm sure if there was any threat to close them the world would come together and make sure they stayed open."
The violence in Iran's key regional ally Syria is also of pressing concern to Saudi Arabia. Mr Cameron suggested Russia should take a tougher line on the issue.
"We've been unable to make progress frankly because there have been some countries on the UN Security Council that have vetoed or threatened to veto proper resolutions on Syria," he said.
The Prime Minister made a gift to King Abdullah, who is a big fan of horses - a saddle from one of the horses that formed the honour guard at last year's wedding of the Duke and Duchess of Cambridge.
The king said he was so delighted with the present that he would put it on display.