President Obama in a wide-ranging press conference Tuesday looked to reassert his clout with Congress and counter growing skepticism about his ability to sway lawmakers 100 days into his second term.

Obama fielded questions on the Boston bombings, chemical weapons in Syria, implementation of his health care overhaul, his inability to close the Guantanamo Bay prison and even National Basketball player Jason Collins coming out as gay.

But the political message behind the rare presidential press conference -- with Congress out of town -- was clear: Obama sought to shake the notion that he can't break through on Capitol Hill.

"Maybe I should just pack up and go home, golly," Obama said sarcastically, adding with a nod to author Mark Twain, "Rumors of my demise may be a little exaggerated at this point."

And the president put full blame on Congress for the unrelenting gridlock in Washington.

"You seem to suggest that somehow these folks over there have no responsibilities and that my job is to somehow get them to behave," Obama said. "That's their job."

Obama's press conference marked the 100th day of his second term, an early measure of his job performance. Over the past three months, Obama has seen his push for new gun restrictions die on Capitol Hill and still faces an uphill battle to implement other centerpieces of his agenda, such as immigration reform.

Foreign events, including evidence that Syria used chemical weapons against anti-government rebels, have also cast a shadow over the president's domestic agenda.

Obama has warned Syria not to cross the red line he established, but said Tuesday only that he would "rethink the range of options that are available to us" if Syrian President Bashar al-Assad ignored his warning.

Critics, like Sens. John McCain, R-Ariz., and Lindsey Graham, R-S.C., pounced on the administration's continued hesitance to intervene in Syria, where roughly 70,000 people have died in a two-year-civil war.

"In explaining his Syria policy today, President Obama was forced to defend the indefensible," the senators said in a statement. "It is also impossible to escape the reality that nothing [Obama] has done has been sufficient to end this conflict."

Obama also faced questions about Guantanamo Bay, the American prison in Cuba where suspected terrorists, or enemy combatants -- held for years by the U.S. -- are now engaged in a hunger strike. He had pledged in his first campaign to shut it down.

"Guantanamo is not necessary to keep America safe," Obama said. "It is a recruitment tool for extremists. It needs to be closed."

However, the president took no blame for Guantanamo remaining open, saying Congress repeatedly blocked his efforts to shutter the prison.

The implementation of Obama's health care reforms is perhaps even more important to the president's legacy than his stalled push for gun control and his calls for immigration reform. Public polling shows that even Democrats are beginning to sour on the health reforms, a trend the president looked to mitigate Tuesday.

Obama said that most Americans are "experiencing the benefits" of those reforms even if "they don't know it."

Shortly before Obama met with reporters, the White House announced that it was shortening the health care application form, conceding that many are confused about how to sign up for the program.