We haven't heard much about rogue states since George W Bush's tenure in the White House ended, but maybe the term should be revived and applied to one of America's closest allies - Saudi Arabia.
The talks on Syria in Vienna have finally got all the relevant international players around the table with Iran taking part along with the Saudis. Following the deal over Tehran's nuclear programme, the US no longer had a good reason to refuse to talk to the Iranians and as Assad's main backers they are crucial to making any progress.
So far so good.
But Saudi Arabia seems to have been doing its upmost to provoke the Iranians into walking out.
Ahead of the talks, the Saudi Foreign Minister, Adel al-Jubeir, gave media interviews saying Iran had to accept Syrian President Assad's removal - interesting, given how Saudi diplomats are usually pretty media shy.
Then when the talks started it appears al Jubeir went out of his way to provoke his Iranian counterpart, Javad Zarif, and there was a blazing row.
Under King Salman's predecessors, Saudi Arabia pursued a cautious foreign policy and shunned the limelight.
No longer.
Although King Abdullah did send troops into neighbouring Bahrain in 2011 during the so-called Arab Spring to put down unrest among the country's Shia majority, since his successor ascended to the throne in January this year he has taken this regional activism to a different level.
Salman appointed his favourite son, the young and inexperienced, Prince Mohammed bin Salman al Saud, Defence Minister. The Saudis promptly launched a direct military intervention in the civil war over the country's southern border in Yemen. With air and some ground forces, the Saudis are leading an alliance of Sunni states trying to crush the Shi'ite Houthi rebels the Saudis accuse of being Iranian proxies.
Many of the more than 4,500 civilians killed so far in the fighting have died in air strikes and recently - in a gruesome rerun of what happened last month in Afghanistan - a Médecins Sans Frontières hospital was hit. The UN says 39 medical facilities have been struck - and possible war crimes committed - in Yemen since the intervention started, although the Saudis deny they are responsible.
Saudi-led forces have imposed a blockade on Yemen though and according to the UN, this is causing a humanitarian crisis as almost 13 million people - half the population - are now short of food, medicine and fuel.
Credible reports indicate the new Saudi government also escalated support - in arms and money - for Syrian rebel groups, including those allied to the al Qaeda-affiliated al Nusra Front. This is thought to have been crucial to the rebel advance which led to Russia's intervention to prop up President Assad in September.
The new Saudi leadership, unnerved by the prospect of US rapprochement with Iran following the nuclear deal and angered by President Obama's sudden U-turn in 2013 when he called off American military strikes on Assad's forces at the last minute, has become markedly less pliant to US wishes.
Like Washington's other close ally in the region, Israel, Saudi Arabia is doing its own thing and Obama, faced with a determined friend, seems largely content to let the tail wag the dog.
The Americans have turned a blind eye to Saudi links to rebels Washington doesn't consider "moderate" enough to merit its own backing. The US has also supplied arms and intelligence to support Riyadh's campaign in Yemen.
While Washington says Assad's use of indiscriminate force against civilians has put him beyond the pale, the moral and diplomatic credibility of its position is undermined by its failure to oppose what the Saudis are up to around the region.
Try a little exercise. Imagine what President Obama and Secretary of State Kerry would have said and done if it were Iran launching air strikes on Yemen and blockading its ports.
If the US is serious about restoring stability to the Middle East and protecting the rights of civilians there, it should be reining in the Saudis in Yemen, not aiding and abetting them.
While on Syria, the Americans should take the Saudis to one side and make it clear to them they should play nice at the talks so as not to extinguish the glimmer of hope for political progress that's appeared since Russia intervened directly in the conflict.