Concerned over Congolese President Joseph Kabila's apparent attempts to cling to power, United States officials are pushing for sanctions against his inner circle but running into opposition from European powers wary of moving too quickly.

Kabila is ineligible to stand in Democratic Republic of Congo's next election due in November, after serving two elected terms. Opponents accuse him of plotting to hold onto power by delaying the poll or even changing the constitution to remove the term limit, as several African leaders have done.

His government says it is unlikely to be able to organise the vote on time, and the electoral commission has said the delay could last 16 months. Senior Kabila ally Henri Mova Sakani on Saturday raised the possibility of a constitutional referendum on the number of terms he can serve.

Any such move risks triggering further violence in Congo, which has never had a peaceful transition of power. Donors worry about a repeat of the regional conflict in eastern Congo between 1996 and 2003, when millions of people died and more than a half-dozen countries were sucked into the fighting.

"This is a historic moment because Congo is such an important part of Africa," Senator Edward Markey, the Africa subcommittee ranking Democrat, told Reuters. "They are going to be looked to for leadership or a failure of leadership."

Protests against a potential delay have already turned violent and authorities have arrested dozens of critics of Kabila, who took power when his father was assassinated in 2001.

The resolution last month by three senior Democrat senators, including Markey, calls on President Barack Obama to join with international partners "to impose targeted sanctions on those officials ... who are responsible for violence and human rights violations and undermining the democratic processes or institutions of DRC, including visa bans and assets freezes."

US officials, including the State Department's special envoy to Africa's Great Lakes region, Tom Perriello, and several senators, are considering sanctions against Congolese officials, for the moment mostly lower-level people in the security forces.

The Senate's Africa subcommittee will hold a hearing on June 8 on US sanctions policy in sub-Saharan Africa. Senator Jeff Flake, the subcommittee's chairman, told Reuters he had discussed targeted sanctions with State Department officials.

The American Congress is pushing President Barack Obama's administration to act unilaterally if it must.

Little impact without EU

But without the EU, sanctions may have little impact since officials in Congo, a former Belgian colony, are thought to have most assets in Europe. The European Union is divided on the subject, and even nations that support sanctions want to exhaust other options first.

"The assessment ... is that we still have a little bit of time to see what is going to happen in DRC," one Western diplomat posted to Washington said.

A European diplomat based in Kinshasa said European thinking is that sanctions threats would "have the best effect when they serve as a warning, not having to be implemented".

Within the EU, Britain is among those leaning toward sanctions with Spain and Italy more reluctant, diplomats say.

The Washington-based diplomat suggested that, as is often the case, commercial interests may play a part in some calculations. A Spanish-led consortium is one of two finalists to develop a $14 billion segment of the Grand Inga hydroelectric project, meant to produce 44,000 MW in all.

Spain's ACS, which is in the consortium, declined to comment. The Spanish Foreign Ministry said it had no comment.

Other EU states also question the efficacy of actually going through with sanctions. The concern is that they "would put him [Kabila] in a corner right now and actually make him more defiant and probably make it even more complicated to have ... substantial dialogue," the Washington-based diplomat said.

Veto-wielding Russia and China

"We hope to coordinate with the Europeans and that they would follow suit quickly," one US official said.

The vast wealth contained in Congo's forests and the minerals underneath them has often divided world powers since its independence in 1960, when the United States and the former Soviet Union vied for Cold War influence.

Extra UN sanctions beyond current travel bans and asset freezes related to conflict in eastern Congo would not get past veto-wielding Russia and China, Congo's top trading partner.

Meanwhile, the country's African neighbours, who analysts think carry the greatest influence, have remained silent.

Congo's government has bristled at talk of sanctions. In a statement last month, foreign minister Raymond Tshibanda denounced the "selective application" of sanctions threats, when the presidents of Rwanda and the smaller neighbouring state Congo Republic have already changed their constitutions to let themselves stand for third terms.

Last month allies of Moise Katumbi, Kabila's main political rival, visited Washington to plead for sanctions.

Stephanie Wolters, a Congo analyst at the Institute for Security Studies in Pretoria, said US sanctions could send an important message but warned that it was also a risky strategy.

"The more isolated the government becomes, the harder it will be to manage potential fallouts of the growing crisis," she said. "European countries are worried about just that."