U.S. President Barack Obama and Turkish Prime Minister Recep Tayyip Erdogan Tuesday discussed the need to "increase pressure" on the Syrian regime to aid the pro-democracy protests.

The two leaders "talked about the need to increase pressure on the Assad regime, in order to lead to an outcome that is responsive to the aspirations of the Syrian people," a White House official said.

U.S. President Barack Obama on Tuesday called on Turkey and Israel to repair their ties strained by a crisis over a deadly 2010 flotilla raid.

"The president underscored his interest in seeing a resolution of that issue between those two countries who are both allies of ours, and encouraged them to work towards that end," said a top White House advisor said.

The United States is increasingly convinced Syrian President Bashar al-Assad will be overthrown and is preparing for a possibly violent aftermath, the New York Times reported Tuesday.

The newspaper said Washington is quietly working with Turkey to plan for a post-Assad future that could see Syria's various ethnic groups battle for control of the country, potentially destabilizing neighboring states.

A powerful bomb rocked the center of Turkish capital Ankara on Tuesday, killing three people and injuring at least 15, the interior minister said, as immediate suspicion fell on Kurdish separatists.

"Three citizens were killed and 15 were injured, five of whom are in critical condition," Interior Minister Idris Naim Sahin told Turkish television.

U.S. Secretary of State Hillary Clinton here on Monday urged Turkey to defuse tension and repair strategic ties with Israel as Washington values them both as allies, U.S. officials said.

Washington has expressed mounting concern about the bitter row between Turkey and Israel over a May 2010 Israeli commando raid on an aid flotilla heading to the Gaza Strip that left nine Turks dead.

Turkey's energy minister said Monday Ankara would consider a proposal from the United States to build a nuclear power plant in the country's north.

"If a proposal comes from the United States, we could evaluate it but so far, no concrete proposal has been made to us," Energy Minister Taner Yildiz told reporters.

Israel said on Monday it was withdrawing its police representative from Turkey and ending bilateral cooperation between their forces as the diplomatic crisis between the two former allies deepened.

"Public Security Minister Yitzhak Aharonovitch has ordered the transfer to Bucharest of the Israel Police representative in Ankara," ministry spokesman Tal Volovich told Agence France Presse.

A Turkish military cargo plane dropping humanitarian aid over the Libyan town of Bani Walid came under fire from the ground, the Turkish news agency Anatolia reported Monday.

The incident happened on Saturday when one of two Turkish C-130 transport planes parachuting 22 tons of aid to residents, was fired on, the agency said, citing a journalist on the plane.

Turkish Prime Minister Recep Tayyip Erdogan said Monday Ankara would start offshore gas drilling off the divided island of Cyprus "very soon" after the Greek Cypriots said they had already begun.

"We will start this within our exclusive economic zone very soon, possibly this week," Erdogan told reporters.

Turkey's top diplomat predicted in an interview published Sunday that his country would form an alliance with a reformed Egypt, creating a new democratic axis of power in the Middle East.

"This is what we want," Turkish Foreign Minister Ahmet Davutoglu told The New York Times.