Republican House Speaker John Boehner said Wednesday that his chamber planned to "file suit in the coming weeks" against President Barack Obama for abuse of executive power.

Obama's Republican foes have long accused him of exceeding the regulatory boundaries laid out under the U.S. Constitution, following a series of executive actions taken by the president.

Vice President Joe Biden spoke with Ukraine's president Tuesday after pro-Russian insurgents downed an army helicopter against ceasefire orders from their commander, the White House said.

The chopper downing, in which nine Ukrainian soldiers were killed, could torpedo hopes that Ukraine's Western-backed President Petro Poroshenko -- having ordered a one-week unilateral ceasefire Friday that the rebels accepted on Monday -- will be able to negotiate an end to 11 weeks of violence that has claimed 435 lives, according to U.N. figures and an Agence France Presse count.

U.S. President Barack Obama on Monday warned Vladimir Putin that Russia would face new sanctions if it failed to both stop the flow of weapons into Ukraine and halt support for separatists.

The White House said that Obama delivered the warning in a telephone call with the Russian leader, in which he called for "concrete actions" by Moscow to de-escalate the situation.

Russian President Vladidmir Putin and his U.S. counterpart Barack Obama on Monday expressed "serious concern" over the advances of jihadists from the Islamic State of Iraq and the Levant (ISIL) in Iraq.

"The Russian leader expressed support for Baghdad's efforts in the fight against Islamists and bringing about peace and stability in the country," said the Kremlin statement after phone talks between to two rivals, adding the two leaders also discussed Syria and Iran's nuclear program.

U.S. President Barack Obama has warned that extremist militants who have surged through Iraq in a lightning and brutal offensive could also destabilize other countries in the volatile region.

The jihadist Islamic State of Iraq and the Levant (ISIL) is rampaging towards the capital Baghdad in its bid to create an Islamic state that will incorporate both Iraq and Syria.

Sunni militants advanced through west Iraq after seizing a strategic Syria border crossing, as U.S. Secretary of State John Kerry arrived in the region Sunday aiming to bridge widening rifts.

The latest assaults saw the security forces making "tactical" withdrawals in the face of an insurgent onslaught that has displaced hundreds of thousands and alarmed the world amid fears Iraq could tear itself apart.

U.S. President Barack Obama warned Friday that no amount of U.S. firepower could keep Iraq together if its political leaders did not disdain sectarianism and work to unite the country.

Obama told CNN, a day after announcing the dispatch of 300 special forces advisors to Iraq following a lightning advance by extreme Sunni radicals, that American sacrifices had given Iraq a chance at a stable democracy, but it had been squandered.

U.S. President Barack Obama said Friday that he is badgering his staff to line up a trip to New Zealand, after holding talks with his golfing buddy, Prime Minister John Key.

Obama and Key met for talks in the Oval Office on trade, security and economic issues, but the conversation also turned to their shared passion for the links and Obama's travel plans.

France and the United States on Friday urged Moscow to help de-escalate the Ukraine crisis or face "new measures" by the Western powers, the French presidency said in a statement.

French leader Francois Hollande spoke by phone with U.S. President Barack Obama and the two called on Russia "to quickly appeal to the armed separatist groups (in east Ukraine) to halt their military actions".

U.S. President Barack Obama said Friday he hopes to have an agreement on framing a vast pan-Pacific trading block by the time he makes his next visit to Asia in November.

The Trans-Pacific Partnership (TPP) would encompass 40 percent of the global economy and include 12 nations. Talks on setting up the pact have been delayed by intricate market access negotiations between Japan and the United States.