U.S. President Barack Obama on Monday hailed "successful" Ukrainian elections that saw pro-Westerners score a big win in parliament, and blasted Russia for preventing voters in the east from casting their ballots.

Politicians were hard at work to build a ruling coalition, with initial results showing Prime Minister Arseniy Yatsenyuk's People's Front and the Petro Poroshenko Bloc neck and neck with about 22 percent of votes each.

U.S. President Barack Obama congratulated his Brazilian counterpart Dilma Rousseff on her re-election Monday, the day after the left-wing incumbent won a narrow victory in a presidential run-off vote. 

"Brazil is an important partner for the United States and we are committed to continuing to work with President Rousseff to strengthen our bilateral relationship," the White House said.

President Barack Obama cast his ballot Monday during a visit in his hometown of Chicago two weeks ahead of November 4 mid-term elections.

"I love voting. Everybody in Illinois, early vote. It's a wonderful opportunity," Obama said after submitting his vote at the Martin Luther King Jr Park & Family Entertainment Center.

U.S. President Barack Obama called his Turkish counterpart Recep Tayyip Erdogan and they pledged to step up the fight against the Islamic State group in Syria, the White House said Sunday.

Kurdish fighters have been under IS assault for more than a month around Kobane, which has become a key prize as it is being fought under the gaze of the world's press massed just over the border in Turkey.

U.S. Secretary of State John Kerry and a top Chinese official had "candid exchanges" over several contentious issues dogging relations between Washington and Beijing, an American diplomat said Saturday.

The pro-democracy protests in Hong Kong, human rights, cyberspying and disputes in the South China Sea -- all areas where the two nations have clashed -- were on the weighty agenda in talks between Kerry and visiting Chinese State Councillor Yang Jiechi.

Ukrainian President Petro Poroshenko on Thursday discussed the crisis in his country's east with U.S. President Barack Obama before jetting off for talks with Russia's Vladimir Putin aimed at resolving the conflict.

The two presidents stressed that the battered ceasefire Kiev inked with pro-Moscow rebels in the east "must be strictly maintained and observed by all parties" and discussed the need for Kiev to reestablish control over its border with Russia, the Ukrainian presidency said in a statement.

Hillary Clinton hit the campaign trail Wednesday in support of a Democratic Senate hopeful, but she sounded every inch like the prospective frontrunner for the 2016 presidential race.

President Vladimir Putin accused his US counterpart Barack Obama of a hostile approach towards Russia, warning in a Cold War-style tirade that Moscow would not be blackmailed by the West over Ukraine.

Putin fired off his combative comments shortly before he arrived amid tight security to a red carpet welcome in Belgrade, seeking to cement Russia's influence in its loyal European ally.

A rising number of Americans think the battle against the Islamic State group should broaden to include U.S. ground troops, according to a poll published Wednesday.

U.S. President Barack Obama vowed to continue his country's humanitarian assistance to Jordan, Lebanon and Turkey to help those countries bear the burden imposed by the large influx of Syrian refugees.

The three countries “are obviously bearing an extraordinary burden from the displaced persons not just recently over the last few months, but for several years now as a consequence of the civil war in Syria,” Obama said at the end of a meeting for military leaders from more than 20 partner nations in the coalition to degrade and destroy Islamic State of Iraq and the Levant (ISIL) in Washington.