From Washington, this is VOA news. I'm David DeForest reporting.

The Russian Air Force Tuesday launched a major operation in Syria's Idlib and Homs provinces. The Defense Ministry said the operation included warplanes from Russia's aircraft carrier which recently arrived in the Mediterranean.

Russian media say the airstrikes were aimed at Islamic State militants and fighters from the Nusra front.

In Washington, the State Department strongly criticized Russia for the new attacks.

Meanwhile, Syrian government aircraft renewed barrel bomb attacks on the city of Aleppo.

United Nations agencies are warning of food shortages in Syria. Lisa Schlein reports.

The U.N. agencies blamed the deteriorating food situation in Syria on widespread insecurity and unfavorable weather conditions in parts of the country. Those factors, they say, are preventing farmers from accessing their land and making it difficult for them to earn a living.

They warned rising prices and lack of fertilizer and seeds may force many farmers to abandon their land unless they receive immediate help.

Lisa Schlein, Geneva.

President Obama was in Greece Tuesday, assuring America's European allies that the U.S. will retain its commitment to NATO under the presidency of Donald Trump.

On his last foreign trip as president, Mr. Obama said NATO (quoting now) "provides significant continuity even as we see a transition of government in the United States."

"I still don't feel responsible for what the president-elect says or does. But I do feel a responsibility as President of the United States to make sure that I facilitate a good transition." :President Obama speaking in Greece.

The U.S. leader also called on NATO members to spend more money on defense.

This is VOA news.

U.S. President-elect Donald Trump and Vice President-elect Mike Pence Tuesday discussed key appointments in their new administration.

Aides are signaling that former New York City Mayor Rudy Giuliani could be named secretary of state. U.S. media reports say retired Army General Michael Flynn, once the head of the U.S. Defense Intelligence Agency, is a possible pick as national security adviser. Alabama Senator Jeff Sessions could be named secretary of defense or attorney general.

Trump has more than 4,000 jobs to fill in the U.S. government as he prepares to take office January 20.

Members of the U.S. House Republican conference convened for leadership elections Tuesday. Republicans easily renominated Paul Ryan to be their leader.

"We're on the same page. We're working hand in glove and we're going to make sure that this is a very successful administration. But more importantly, we're going to make sure that the voices we heard from this election from the American people are acted upon."

In January, the new Congress will confirm Ryan as speaker for his first full term.

As Republicans presented a unified front, House Democrats met just down the hall and showed disunity.

A leadership election was delayed until Thursday. At least one representative plans to challenge current leader Nancy Pelosi for the top leadership spot.

The election of Donald Trump is casting a cloud over the conference of the U.N. Framework Convention on Climate Change.

U.S. Secretary of State John Kerry is to deliver a speech at the convention in Morocco on the importance of fighting climate change.

President-elect Donald Trump during the recent campaign vowed to rip up the Paris Agreement on climate change.

Trump's election is also expected to overshadow the Asia-Pacific Economic Cooperation meeting scheduled for later in the week. Many leaders are concerned about Trump's opposition to the U.S.-led Trans-Pacific Partnership, which still has not been approved by the U.S. Congress.

Russian prosecutors charged Economic Development Minister Alexei Ulyukayev with extortion Tuesday and requested that he be placed under house arrest. It is Russia's highest-level corruption case in decades. Ulyukayev's lawyer said he denies all of the charges.

Analysts and observers question the charges as politically motivated and say the arrest more likely exposes an internal Kremlin battle between those for and against more state control of the declining Russian economy.

An investigative committee says Ulyukayev [has detained] was detained late Monday after a sting operation carried out by Russia's Federal Security Services.

The committee says the minister received $2 million from a state oil company in return for a positive assessment on a purchase deal.

In Washington, I'm David DeForest.

That's the latest world news from VOA.