By Will Dunham
WASHINGTON, June 10 (Reuters) - The United States on Tuesday condemned the seizure of the Iraqi city of Mosul by Sunni Islamist insurgents, calling the situation "extremely serious" and urging fractious political groups to fight Iraq's enemies together.
State Department spokeswoman Jen Psaki said the takeover of Iraq's second biggest city in the last 48 hours by forces from the Islamic State of Iraq and the Levant showed the deterioration of security in the country.
Washington has supplied large amounts of weaponry to Iraq since pulling its forces out in 2011, but Baghdad has failed to heal festering sectarian and political divisions and to curb instability spilling over from the Syrian civil war.
"There's no question that unity - and all sides and officials in Iraq working together - is the only way that they can be successful here," Psaki told reporters.
ISIL originated as an Iraq-based affiliate of al Qaeda. Recently the group, fighting to set up an Islamic state in parts of Iraq and Syria, has been denounced by al Qaeda's central leadership for apostasy and excessive violence.
Psaki said U.S. officials were tracking events closely in coordination with Prime Minister Nuri al-Maliki's government and other officials, including Kurds in their semi-autonomous northern region.
"The situation remains extremely serious," she said in a statement.
White House spokesman Josh Earnest urged Maliki to do more to meet the needs of Iraqis who complain they are marginalized by his Shi'ite-led government.
In recent years the Obama administration has taken a largely hands-off approach to Iraq, which the United States invaded in 2003 to oust Saddam Hussein.
Over the last year the Syrian conflict rekindled insurgent violence and Washington accelerated efforts to smooth over differences between Iraq's Sunnis, Shi'ites and Kurds and provided arms requested by Maliki.
U.S. ARMS SUPPLIES
Psaki said this included 300 Hellfire missiles, small arms and tank ammunition, rockets, machineguns and rifles.
She said the United States also delivered Bell IA-407 helicopters last year, and surveillance equipment is set for delivery this summer. There is also a proposed agreement to sell Iraq attack helicopters.
A senior U.S. national security official said Kurdish leaders were considering a request by Maliki to send Kurdish peshmerga fighters to Mosul.
Jessica Lewis, an analyst at the Institute for the Study of War in Washington, said Washington had underestimated the threat posed by ISIL.
"This is a conventional military enemy that is pursuing a state vision that involves the destruction of Iraq and Syria as we know them. It's not just a terrorist threat," she said.
Republican Senator John McCain said the takeover of Mosul reflected President Barack Obama's failure to leave a U.S. force in Iraq to help assure stability.
"There's no doubt that we could have left troops behind, as we have in Korea and Germany and Bosnia, and didn't, and so it is now chaos, and so you will see greater and greater attacks and ... chaos in Iraq," McCain told reporters. (Additional reporting by Steve Holland, Mark Hosenball, Missy Ryan, Phil Stewart and Patricia Zengerle; Editing by David Storey and Mohammad Zargham)