Presidential tours are always expensive, but especially so when the country being visited is, like Kenya, the scene of regular terrorist attacks.

U.S. and Kenyan officials are fixated on making sure al-Qaida's Somali-led affiliate, the Shebab, cannot violently disrupt the U.S. presidential visit this week.

U.S. President Barack Obama spoke with his Chinese counterpart Xi Jinping to thank him for Beijing's work on the deal to curtail Iran's nuclear program, the White House said Tuesday.

In a conversation Monday, the two leaders also agreed it was important to keep working together to ensure implementation of the historic accord reached last week in Vienna, the White House said in a statement.

U.S. Defense Secretary Ashton Carter met Prime Minister Benjamin Netanyahu on Tuesday to try to ease tensions over the Iran nuclear deal, as the Israeli leader urged lawmakers in Washington to reject the hard-won agreement.

The two men greeted each other with a long handshake before entering the meeting that lasted nearly two hours, making no comment about the tensions over the nuclear accord that Netanyahu has harshly condemned.

Barack Obama will welcome Nigeria's freshly elected president to the White House Monday, lending a personal endorsement after the country's first ever democratic transition.

Obama's administration has faced criticism for not including the continent's most populous country on a Africa tour later this week that will take in Kenya and Ethiopia.

The landmark deal on Iran's nuclear program that Russia helped steer through marathon talks is a diplomatic fillip for Moscow which will boost trade with Tehran but could also hit much-needed energy revenues, analysts said.

Iran and the P5+1 group -- Russia, the United States, China, Britain, France and Germany -- struck an agreement on Tuesday that would progressively lift economic sanctions against Tehran in exchange for limitations on its nuclear program.

U.S. President Barack Obama won't be visiting his Kenyan relatives in their home village in the west of the country during his trip to Kenya later this month, the U.S. ambassador said.

"I can confirm that unfortunately President Barack Obama will not travel to Kogelo during his visit to Kenya," Robert Godec told Kenya's KTN news channel in an interview late Thursday.

Washington and London sought Thursday to ease concerns over the Iran nuclear accord as the country's supreme leader warned that major powers are not to be trusted over its implementation.

As part of an international charm offensive, British Foreign Secretary Philip Hammond was to meet Israeli Prime Minister Benjamin Netanyahu, who strongly opposes the landmark accord stuck on Tuesday in Vienna between Iran and world powers led by Washington.

President Barack Obama spoke by phone Wednesday with Vladimir Putin, thanking his Russian counterpart for his role in reaching a deal on Iran's nuclear program.

U.S. ties with Russia have been strained to breaking point over the war in Ukraine, but Russia was an "important" part of the group of nations that negotiated the deal with Tehran.

U.S. President Barack Obama on Wednesday said that Iran had a role to play in ending the bloody civil war in Syria.

Saying there would be no military solution to a conflict that has drawn in a host of regional actors, Obama said Iran was one important player.

U.S. President Barack Obama sought Wednesday to defend a ground-breaking deal to curb Iran's nuclear program from a tide of criticism, saying "profound differences" would remain with the Islamic republic.

Amid fears Washington was seeking to cozy up to its long-time foe with an agreement that might not stand the test of time, Obama said: "Even with this deal, we will continue to have profound differences with Iran."