BRUSSELS (Reuters) - The European Union imposed asset freezes and visa bans on 15 more Russians and Ukrainians on Monday as part of expanded sanctions on Moscow over its actions inUkraine.

The decision brings to 48 the number of people that the EU has put under sanctions for, it says, helping undermine Ukraine's territorial integrity.

The names of the 15 will not be made public until they are published in the EU's Official Journal on Tuesday.

EU diplomats said they would not include the heads of Russian energy giants such as Rosneft's Igor Sechin, who was included on a new U.S. sanctions list on Monday.

The EU decision coincided with a White House announcement that the United States was imposing sanctions against seven Russians and 17 companies linked to Russian President Vladimir Putin.

The United States has been much more aggressive in the penalties it has imposed on Russia than has the 28-nation European Union, which depends heavily on Russia for energy.

The EU has so far only put sanctions on individuals, not companies. EU ambassadors, meeting on Monday, discussed the need to broaden the legal basis to enable the bloc to put sanctions on companies, diplomats said.

The European Commission is drawing up a list of tougher economic sanctions, possibly affecting trade or the energy or finance sectors, that could be imposed on Russia.

The EU is split between countries in favor of stronger action, including Britain, France, Poland, Sweden,Denmark, the Czech Republic and the Baltic countries, and those who are reluctant, such as Italy,Greece, Cyprus, Bulgaria, Hungary, Luxembourg, Austria, Spain, Portugal and Malta.

"The main issue is to see how best to get a diplomatic resolution to the crisis, what is necessary to entice Russia to sit around the (negotiating) table. Sanctions are not an end in themselves," one diplomat said.

Another diplomat said he believed the EU would eventually decide on tougher sanctions against Russiaif the situation in Ukraine continued to deteriorate.

"I can't imagine that if the Americans act that the Europeans won't do anything," he said.