WASHINGTON - After his efforts at diplomacy on the international stage last week, President Barack Obama faces some particularly daunting foreign policy decisions about the Afghan war, a nuclear Iran and an elusive Middle East peace.

The world's problems only add to the issues plaguing Obama at home: nearly 10 percent unemployment and a fractious Congress squabbling over his plans to overhaul healthcare and curb the gas emissions that are warming the planet.

Having made his debut at the United Nations and hosted the Group of 20 financial summit in Pittsburgh, Obama has returned to Washington to a three-month make-or-break period before lawmakers start campaigning for 2010 elections.

He's been setting the stage for progress on a lot of issues where the progress is going to be very difficult, said George Perkovich, a nuclear policy expert at the Carnegie Endowment for International Peace.

None of these problems was solved last week.

Having brokered a handshake rather than a breakthrough between Israeli and Palestinian leaders, Obama will have his Middle East envoy, George Mitchell, carry on negotiating and Secretary of State Hillary Clinton report back in October.

AFGHANISTAN, IRAN

On Afghanistan, Obama will weigh options with aides in the face of disagreement over a request from General Stanley McChrystal, the top U.S. and NATO commander in Afghanistan, for tens of thousands more U.S. troops.

A leak to the media of McChrystal's bleak assessment of the Afghan war effort drew charges from Republicans last week that Obama was indecisive, while his fellow Democrats fear becoming mired in a Vietnam-like war now eight years old.

The question comes, is there an alternative to this long-term, comprehensive, full-blown counterinsurgency strategy which (McChrystal) has laid out? Democratic Senator Dianne Feinstein asked on Fox News Sunday.

I hope there is, because I do not believe the American people want to be in Afghanistan for the next 10 years, effectively nation-building, Feinstein said.

Iran test fired several missiles on Sunday, adding to the tension between Tehran and the West over the Islamic republic's nuclear program. Iran meets the United States and five other world powers for talks on Thursday as part of Obama's drive to resolve conflicts through negotiation.

At the G20 summit on Friday, Obama joined the leaders of France and Britain in issuing a stern warning to Iran as they accused it of working in secret to build a uranium enrichment plant near the holy city of Qom.

The disclosure of the plant and new signs from Russia that it might support sanctions bolstered Obama's foreign-policy credentials. He also held an extensive discussion on Iran with Russian President Dmitry Medvedev on the sidelines of last week's U.N. General Assembly meeting.

It's clearly not good for the Iranians, Perkovich said. It puts them under more pressure.

BUSH PLANS SCRAPPED

Just before the U.N. meeting, Obama announced he would scrap Bush administration plans for a missile defense shield in eastern Europe and replace them with another plan less irritating to Moscow.

The administration insisted there was no quid pro quo between the missile shield decision and Russia's new tougher stance on Iran but analysts said Obama's move increased the chances of Moscow's cooperation.

The sanctions which might be imposed on Iran could be sharply influenced by the disclosure of the Qom facility, said Anthony Cordesman, a military analyst at the Center for Strategic and International Studies.

Crediting Obama for his handling of the Iran issue, Cordesman added: It is striking that he does not close off his options and he certainly has not over-reacted.

Cordesman, who served on a panel that advised McChrystal's Afghanistan assessment, criticized Obama on that issue, saying that he was running out of time to deliberate a crisis that had festered under his predecessor Bush.

The president came to office (in January) in a crisis and this is now September and it will soon be October, Cordesman said. There are times you can't keep studying the problem.

White House National Security Adviser James Jones told the Washington Post that Obama planned at least five intensive meetings on Afghanistan over the coming weeks, with the first starting on Tuesday.

The meetings will begin with an assumption McChrystal's strategy is correct and there will be a freewheeling discussion with nothing off the table, Jones said.

Republican Senator John McCain, who lost to Obama in the November 2008 presidential election, agreed with Cordesman that time was of the essence and said he spoke to Obama on Saturday about his view that more troops were needed.

I sympathize with the president. The base of his (Democratic) party, the left base of his party, is opposed, McCain said. People are weary of this conflict ... It's the toughest decision a president has to make.

(Editing by Howard Goller and Chris Wilson)