West Texas Intermediate crude climbed to the highest level in nine months on concern that tension in the Middle East will reduce exports.

Prices headed for a second weekly gain after President Barack Obama was said to authorize lethal military aid to rebel groups in Syria. The administration said yesterday that it had confirmed the use of chemical weapons by President Bashar al-Assad’s forces during the civil war. Assad has received support from allies including Iran, the sixth-biggest OPEC oil producer.

Obama is authorizing the provision of small arms and ammunition to the Syrian opposition under a classified order instructing the Central Intelligence Agency to arrange delivery of the weapons, according to a U.S. official familiar with the decision who asked not to be identified discussing the move.

The decision to arm the opposition was prompted by rebel losses rather than by the U.S. confirmation, announced yesterday, that Assad’s forces had used chemical weapons, according to the official familiar with the move.

Syria borders both Iran and Iraq, countries that together hold almost a fifth of the Organization of Petroleum Exporting Countries’s output capacity, according to estimates.

Iranians went to the polls today to choose a successor to President Mahmoud Ahmadinejad who may determine whether the international isolation of world’s fourth-largest oil-reserve holder will continue. Voting was extended by three hours to 9 p.m. local time, state-run Press TV reported.

WTI for July delivery climbed 92 cents, or 1 percent, to $97.61 a barrel at 11:47 a.m. on the New York Mercantile Exchange. It touched $98.25, the most since Sept. 17, breaching the prior 2013 high of $98.24 on Jan. 30. The volume of all futures traded was 42 percent above the 100-day average. Prices are up 1.9 percent this week.

Brent for August settlement increased $1.01, or 1 percent, to $105.96 a barrel on the London-based ICE Futures Europe exchange. Volume was 17 percent below the 100-day average for the time of day.

Brent’s premium to WTI for August delivery widened to as much as $8.32 from yesterday’s $7.56 based on July contracts.