U.S. Vice President Joe Biden will meet top European leaders in Brussels and Munich this week to discuss boosting security and financial aid to Ukraine and tightening economic sanctions on Russia, senior U.S. administration officials said.

Biden's visit, which will include trilateral talks with Ukrainian President Petro Poroshenko and German Chancellor Angela Merkel, coincides with a debate in Washington over whether to provide weapons to Ukraine in its fight against Russian-backed separatists.

"All of these issues will be on the table: financial assistance, increasing pressure through sanctions, and how we can most effectively provide security assistance to Ukraine," a senior official told reporters on Wednesday, speaking on condition of anonymity.

"Our sanctions policy, as well as our security assistance, are aimed at changing the incentive structure facing Russia and encouraging them to settle this conflict at the negotiating table," the official said.

President Barack Obama's nominee for defense secretary, Ashton Carter, told Congress on Wednesday he was in favor of supplying defensive arms to Ukraine.

His remarks contrasted with a more cautious approach from Obama's deputy national security adviser, Ben Rhodes, who stressed the risk of getting into a "tit-for-tat" exchange with Russia and said economic sanctions were the best way to influence Moscow.

The United States has provided some non-lethal military equipment to Ukraine, but has declined up to now to send arms, saying it does not want to be drawn into a proxy war with the Russians.

Secretary of State John Kerry will visit Kiev on Thursday for talks with the government, and Merkel will be in Washington on Monday for talks with Obama at the White House.

"We're entering obviously what is a very intensive period of diplomacy," a second senior official said.

On Friday in Brussels, Biden is slated to meet with European Council President Donald Tusk, European Commission President Jean-Claude Juncker, and other European Union leaders. He will also speak at the annual Munich Security Conference.

In Munich, Biden also is expected to meet with Iraqi Prime Minister Haider al-Abadi and the head of Kurdistan's Security Council, Masrour Barzani, to talk about the fight against Islamic State militants in Iraq and Syria, the officials said.