Kerry said he will be briefing Ukrainian Prime Minister Yatsenyuk shortly, as well European Union leaders.
Kerry said he and Lavrov agreed to stay in touch both on Ukraine and Syria and Iran and other issues.
There is a better way for Russia to pursue its interests in Ukraine, Kerry said, adding that the U.S. does recognize Russia has legitimate interests in the county.
Lavrov made it clear President Putin is not prepared to make any decision regarding Ukraine until after the referendum on Sunday, Kerry said. However, the U.S. and international community will not recognize the referendum.
President Vladimir Putin on Friday rejected Western accusations that a referendum on whether Ukraine's Crimea region should join Russia would be illegal, making clear the vote would go ahead as planned on Sunday.
In a telephone conversation with U.N. Secretary Ban Ki-moon, Putin "underscored that the decision to conduct (the referendum) fully corresponds to the norms of international law and the U.N. Charter", the Kremlin said.
According to the Austria press agency, an Austrian court has ordered Ukrainian oligarch Firtash to be held for extradition, Reuters reports.
According to a court spokesman, the court set a 125 million euro bail for Firtash, Reuters reports.
The court in Austria says it still has to make the final decision on whether Firtash will be extradited to the United States, according to Reuters.
A reporter asks if Secretary-General Ban has a message to the people of Crimea regarding the referendum scheduled for Sunday.
Ban responds: "Emotions have been hardened over the forthcoming referendum in Crimea. What I'm concerned is that there should be no such hasty or major decision which may impact the sovereignty, unity and territorial integrity of Ukraine."
A senior United States administration official says hopes the crisis in Ukraine won't pose a risk for cooperation with Russia on the nuclear talks with Iran, Reuters reports.
Speaking to the press, Secretary-General Ban Ki-moon says that "it is clear we are at a crossroads" with the crisis in Ukraine.
"The Security Council has met many times on the matter, but the international community has not yet been able tp deescalate the situation," said Ban. "I urge all concerned to avoid all provocations and hasty decisions in the coming dayss. We must engage in a direct dialogue to pave the way for a domestic diplomats solution."
"Also it has so far proven elusive , but the pat to a peaceful solution is still open," adds Ban. "We must seize it."
Ban says he spoke by phone with Russian President Putin this morning. Ban and Putin discussed the need to work toward a durable political solution and agreed to remain in close touch over the next few days.
According to the Kremlin, Russian President Putin has told United Nations Secretary-General Ban Ki-moon the decision to hold a referendum on Crimea's status is completely in line with international law, Reuters reports.
Lavrov has finished speaking to the media in London.
What happened in Donetsk is 'outrageous' Lavrov said. The Russian Federation does not have any plans to invade Eastern or Southern Ukraine he said, adding that the rights of Russian, Bulgarian and Hungarian people — among others — should be protected.
According to The Associated Press, Lavrov said Russia and the United States do not have a 'common vision' on Ukraine despite the 'useful' talks in London
After the 'legitimate' president in Kiev was 'ousted' there were some issues, Lavrov said, but President Putin instructed his government to continue working with Ukraine, so the country can discuss any issues it has with Russia directly with Russia.
Lavrov said Russia will respect the result of the Crimea referendum and the crisis in Ukraine is not the result of Russia's actions.
According to Germany's Bild newspaper, the European Union and United States visa bans against Russia would target at least 13 Russian officials, including top ministers and people around President Putin, Reuters reports.
According to Interfax, which quoted a navy spokesman, Russian fighter jets and helicopters are holding training exercises over the Mediterranean Sea, Reuters reported a little after 5 a.m. ET on Friday.
Russia's Foreign Ministry says the OSCE mission to Ukraine should be agreed to with leaders of the regions where it will be deployed, Reuters reported Friday a little after 5 a.m. ET.
Crimea may sell Ukrainian energy firm Chornomornaftohaz to a Russian company "like Gazprom" once the regional authorities take control of it, Interfax news agency quoted a Crimean official as saying on Friday.
"After nationalisation of the company we would openly take a decision - if a large investor, like Gazprom or others emerges - to carry out (privatisation)," Rustam Temirgaliev, Crimea's first deputy prime minister, said.
Earlier this week he said Crimea would take ownership of Ukrainian state companies on its territory, including the region's Black Sea natural gas fields, cementing the region's independence before a referendum on joining Russia on Sunday.
A young man was stabbed to death and more than a dozen people were in hospital on Thursday after rival Ukrainian demonstrators clashed in the mainly Russian-speaking eastern city of Donetsk, medical officials said.
In the worst violence since last month's overthrow of Ukraine's Moscow-backed president, hundreds of people waving Russian flags and chanting for Russian President Vladimir Putin scuffled on the central Lenin Square with demonstrators flying Ukrainian flags and condemning Russia's takeover of Crimea.
By late evening, the streets were quiet again.
The local health authority said a 22-year-old local man died of a knife wound and 15 others were being treated in hospital. Organizers of the pro-EU rally, which also denounced Russia's takeover of Crimea, said the dead man was from their group.
Journalists saw police try and fail at times to keep the two sides apart as the rival crowds threw smoke bombs and other missiles. Scattered fights broke out around the square and nearby streets as the demonstrators began to disperse.
Activists opposed to Russia's move in Crimea later said that a further two demonstrators had died, but officials said they had no such information.
Donetsk is the main city in the Ukraine's Donbass industrial heartland, close to the Russian border. Ukrainian officials have accused Russia of supporting groups in the area which favor rule from Moscow and of sending militants over the border.